Water Care

Testing

A hot tub holds a small amount of hot water, and it changes fast. Test before you add anything, and before anyone gets in.

The CDC advises testing a home hot tub at least twice a day. This manual asks for less. It asks for a test before and after every soak, and at least three times a week in any case.

Test kits

• Test strips are quick, but they are coarse. Many read chlorine in steps such as 0, 1, 3, 5 and 10 ppm, so a strip cannot show whether the water is above a 2 ppm minimum. Before a soak at the standard level, a strip is enough when it clearly shows 3 or 5. At the higher level, where the minimum is 3 ppm, a strip is enough only when it clearly shows 5; for 3, use the drop kit. When a strip shows 1, falls between two colour blocks on the chart, or the pH pad shows 7.8, use the drop kit before you decide. The pH pad on a common strip steps from 7.2 to 7.8, so it cannot show 7.6, the top of the routine range; and the hardness pad steps 100, 250, 500, so it cannot check the 200 to 250 ppm calcium range. Both need the drop kit.
• A drop kit has liquid reagents and a sample tube. Use one that reads free chlorine, which means a DPD or FAS-DPD kit. The yellow OTO kits read total chlorine only.
• The stabilizer pad on a strip is coarse too: on a common seven-way strip the colour blocks are 0, 30 to 50, 100 and 150, so a reading between the 30 to 50 block and the 100 block tells you only that you are somewhere between 50 and 100. The drain points in this manual, 80 and 50, both sit in or at the edge of that gap. A black-dot stabilizer test (a turbidity test), where you fill a tube until a black dot disappears, reads them.
• Keep strips and reagents dry, closed and in date.
• “Zero” in this manual means no colour change on the chlorine pad or in the drop test.

Getting a true reading

• Take the sample with the pump running, from below the surface and away from the fittings where water comes back into the tub.
• To check a chlorine dose, test 20 minutes after it went in.
• After adding a balancer (a product that adjusts alkalinity, pH or calcium; Section 08), let the water circulate for 30 minutes before you test again.
• For about a day after an MPS dose (Section 06), total chlorine tests and some strips may read high. A DPD drop test for free chlorine is not affected.
• Tinted water in a new tub makes colours harder to match. Read the strip or tube against a white background.

The diluted test

A very high chlorine or bromine level can bleach the test so that it reads low or blank. Do the diluted test when a reading is low or blank and any of these is true: you know a large dose went in, a weighed dose does not register, there is a chlorine smell, or the wood has started to turn pale. Mix one part tub water with one part distilled water, test for chlorine or bromine only, and multiply the result by 2. If that still reads at the top of the scale or blank, mix one part tub water with four parts distilled water and multiply by 5. If it is still off the scale, keep everyone out and drain part of the water (Sections 10 and 11).

Keep a log

Write down the date, the readings and what you added, every time, and keep a running total of the dichlor added since the last drain. Appendix D is a sheet you can copy. If you call us for help, the log is the first thing we will ask for.

The Sanitizer

The sanitizer for our tubs is sodium dichlor: chlorine granules that you weigh, dissolve in a bucket and add by hand.

Buy granules that list sodium dichloro-s-triazinetrione as the active ingredient (some labels say sodium dichloroisocyanurate) and are sold for spas or hot tubs. Avoid blends with added clarifier, buffer or algaecide. In Canada the label carries a Pest Control Products Act registration number or the words “Scheduled under the Pest Control Products Act”. In the United States it carries an EPA registration number. The label also gives the available chlorine, usually 56% or 62%. The doses in this manual depend on that figure, so check it.

Follow the label for handling, storage, first aid and disposal, and never add more than it allows. The doses in this manual are smaller than the Health Canada model label’s; if your label gives a smaller figure, use the label’s. The model label asks for 3 to 5 ppm in a spa; our standard level is below that, and Section 02 says what that costs you. Its alkalinity range, 100 to 120 ppm, sits inside ours; its calcium range, 150 to 200 ppm, is below ours, which follows the heater and ionizer makers’ 200 ppm minimum. If a label says not to dissolve the product before adding it, do not use that product in a cedar tub.

How to add a dose

1. Test. pH has to be 7.8 or lower before chlorine goes in. If it is higher, lower it first (Section 08). After a soak you can go by the pH reading you took before it.
2. Put on gloves and eye protection. Weigh the dose in a dry plastic cup that is used for dichlor only, on a small digital scale that is kept with the tub chemicals and used for nothing else.
3. Half-fill a clean plastic bucket with tub water. Add the granules to the water and stir until none are left. Do this outdoors or with plenty of ventilation, and keep your face away from the bucket.
4. With the pump running, pour the solution slowly into open water, away from the walls and seats, and away from the stove on a wood-fired tub. On a jetted tub, run the jets for a few minutes with the air controls closed. On a tub without jets, stir the water for a minute with a clean plastic paddle.
5. Leave the cover off and the pump running for 20 minutes. An open tub is a drowning hazard for children and pets. Stay with it, or put the cover back on if you have to leave. If anyone is about to get in, test again first.

The routine dose

After a soak, test and top up to your target even if the reading is still above your minimum. On a day nobody soaks, test, and dose to your target only when the reading is below your minimum. Test at least three times a week in any case. There is no fixed limit on doses in a day once the tub holds chlorine overnight, but every dose adds stabilizer, so do not dose more than the readings call for.

Grams of dichlor for our 6 ft × 4 ft tub (2,327 L, 615 US gal)

These figures are for that tub only, rounded to the nearest gram. For a reading between two rows, multiply the grams per 1 ppm by the ppm you need: from 1.5 ppm to 3 ppm in this tub is 1.5 × 4.2, about 6 g. For any other volume use Appendix B. A level teaspoon of dichlor is roughly 5 g, but spoons vary, so weigh the dose.

Before a long soak, or a soak with several people, bring chlorine up to your target first. Afterwards the reading may be near zero again. Dose to your target again. Do not try to cover heavy use with one large dose.

If chlorine is low

If the reading is zero and it is more than three days since the last dose or the last test that showed any chlorine (whichever is later), or you do not know how long, keep everyone out and follow Section 11 instead of dosing.

1. Dose to your target, wait 20 minutes with the pump running, and test. At or above your minimum, carry on.
2. Still below your minimum: do not dose again. Wait another 20 minutes and test once more, with the drop kit if you have one or a fresh strip. At or above your minimum, carry on. Otherwise:
   • Above zero but below your minimum: nobody in for the rest of the day. Test in the morning (step 3).
   • Zero, or a blank pad, after a weighed dose: do the diluted test (Section 03) first; far too much chlorine also reads zero. If the diluted test reads above 5 ppm, see “Too much sanitizer” in Section 11. If it also reads zero, the dose has been used up: nobody in today, check the log and the product label, and test in the morning (step 3).
3. The next morning, test before you dose. At 1 ppm or more the water held: back to the routine. Under 1 ppm, something is using up the chlorine, and what to do depends on the tub.
   • A new tub (Section 01): expected. Keep to the new-tub routine.
   • First three days of a fresh fill: see Section 10; two such mornings in a row mean a flush, drain and refill.
   • A tub in the Section 11 restart: that section has its own steps. Any other tub: keep everyone out and see “Chlorine will not hold” in Section 12.

A higher-risk household (Read This First) has one stricter rule: after any zero reading, nobody gets in until the next morning’s test reads 1 ppm or more and the soak checks above pass, whatever later readings say; in a new tub, the last bullet below applies instead.

Soaking in a new tub

In a new tub the cedar uses chlorine quickly, and the level can fall while you are in the water. The water is less well protected than in a tub that holds chlorine overnight. A zero reading in the morning is expected in a new tub; the Section 11 rule at the top of “If chlorine is low” applies only after three days without chlorine.

• Dose just before the soak, wait 20 minutes and test. Nobody gets in unless the tub passes the soak checks above.
• Keep the soak to 15 minutes or less.
• Test and dose again as soon as you get out. While the tub is new, no more than two doses in a day, the fresh-fill dose included (twice the normal load on the wood). On a day you plan to soak, skip the morning dose: the dose before the soak is the first of the two and the dose after it is the second, so a new tub gets one soak a day. MPS (Section 06) does not count.
• If anyone who uses the tub is in a higher-risk group, we recommend they do not soak until the tub holds chlorine overnight; the rest of the household may, by the rules above.

Stabilizer

Dichlor contains a stabilizer, cyanuric acid, and every dose leaves a little more of it in the water. We use dichlor on cedar because of the stabilizer, and the stabilizer is also what limits how long you can keep a fill.

Stabilizer holds most of the chlorine in the water in reserve and lets it go as it is used up. Only the part that is not being held is active at any moment. A tub with stabilizer in it, reading 3 ppm, has much less active chlorine against the wood than a tub reading 3 ppm without it. We believe that is easier on cedar.

Every 1 ppm of chlorine added as dichlor leaves about 0.9 ppm of stabilizer behind. It does not break down or evaporate enough to matter, and the filter does not remove it. As it builds up, the same chlorine reading does less work. Past the limit, water can test in range and still sanitize poorly. So drain at 80 ppm, even when the water looks and tests fine.

The rule

• Test stabilizer every two weeks. Test every week in a new tub or with daily use: both add stabilizer fast enough for a two-week gap to pass the drain point. The running total tells you when a test is due sooner.
• At 80 ppm, drain and refill before the next soak if you can, and within a week at the latest (Section 10).
• Keep a running total of dichlor in the log, in the column headed “Dichlor since last drain”. Stabilizer reaches 80 ppm after 156 g of 56% dichlor for every 1,000 L of water, or 141 g of 62%. In our 6 ft × 4 ft tub that is 365 g of 56%, or 329 g of 62%. Appendix B has the figure for other volumes. Drain when the test or the total gets there, whichever comes first. After a partial drain (Section 10), reduce the total in proportion to the water you took out, or leave it as it is and drain early.
• Never add stabilizer or conditioner as a separate product.
• A tub with a ClearBlue ionizer is drained at 50 ppm, not 80. Section 07 gives the reason and the dichlor total.

How long a fill lasts depends on how much the tub is used: a few weeks with daily use, a few months with a few soaks a week. The test and the running total tell you when to drain, not the calendar, apart from the four-month limit and the interval on your chlorine label if that is shorter (Section 10). A new tub dosed twice a day can get there in two weeks.

Fresh fills

New water has no stabilizer in it, so chlorine is at its strongest on a fresh fill. Section 10 has the doses.

Weekly Oxidation

Chlorine kills bacteria. It is slower to clear what people leave in the water: sweat, body oils, lotion and cosmetics. These cloud the water, cause odour and use up chlorine. A weekly dose of oxidizer breaks them down.

The oxidizer is potassium monopersulfate, sold as MPS or non-chlorine shock. It is the only shock treatment used on our tubs. Chlorine shock, also called superchlorination, is never used, because it takes chlorine far above the 5 ppm limit. MPS is not a sanitizer. It adds no chlorine and no stabilizer, and it does not replace the chlorine dose. Use a product whose only active ingredient is potassium monopersulfate. Some labels say potassium peroxymonosulfate, or spell it monopersulphate. Do not use a shock that lists dichlor, calcium hypochlorite or any other chlorine compound.

• Dose once a week, at any time of day that suits you, at the spa maintenance rate on the label or the ceiling below, whichever is less.
• Do not go above 30 g per 1,000 L of a full-strength product, which is 43–45% potassium monopersulfate or about 4.5% active oxygen. In our 6 ft × 4 ft tub that is 69 g. Many spa labels give a higher rate than this. The ceiling wins. For a weaker product the ceiling rises in proportion, to 40 g per 1,000 L for a 32% product, and the label rate still applies.
• Test chlorine before the MPS goes in, so that you know where the level stood. If it is below your minimum, dose to your target first and add the MPS 30 minutes later. Dissolve the MPS on its own in a rinsed bucket. Never put MPS and chlorine in the same bucket. Together they give off dangerous gas (see “Do not mix products”, Section 08).
• Leave the cover off and the pump running for 20 minutes, as you do after a chlorine dose, and nobody gets in until then (Section 04).
• Add a second dose in the same week only after unusually heavy use. An MPS dose called for in Section 11 or 12 takes the place of that week’s dose.

MPS is acidic. A full 69 g dose lowers total alkalinity by 6 to 7 ppm in our 6 ft × 4 ft tub, so expect to add alkalinity increaser every few weeks.

For about a day after an MPS dose, total chlorine tests and some strips may read high. A DPD drop test for free chlorine is not affected. That is why you test before the MPS goes in. Until the next day, go by a drop kit if you have one. With strips only, a strip that shows 5 clears the water at either level; a strip that shows 3 or less does not, because it may be reading high: get a drop-kit reading before anyone gets in, or nobody in that day. If a strip reads above 5 ppm, wait and test again later in the day.

Supplemental Systems

Some of our tubs are fitted with a ClearBlue ionizer or a Clear Comfort CCW25. Both are add-ons. A tub with either one still needs the full chlorine routine in this manual.

What follows is a summary for day-to-day water care. For operation, service and electrical safety, follow the maker’s manual. Ask us before fitting any other water treatment device, such as a salt system, ozone, UV or a mineral cartridge.

ClearBlue ionizer

The ClearBlue passes a small electric current between two metal electrodes, the cell, in the plumbing, which releases copper, silver and zinc into the water as it flows past. ClearBlue says these minerals help control algae and bacteria, and it requires chlorine to be kept in the water as well.

Our tubs are fitted with the ClearBlue Mineral System for hot tubs, model CBI-350 series, and this section follows ClearBlue’s 2026 operating manual. Keep that manual with the tub. That manual gives 0.5 to 5 ppm of free chlorine in a spa once copper is in range, and 3 to 5 ppm until it gets there. That is the range for running the ionizer, not a water safety range, and Health Canada’s 3 to 5 ppm applies with or without an ionizer. This manual’s minimum and target apply with the ClearBlue fitted. Do not run lower because the ClearBlue manual allows it.

• Copper is the reading that tells you how the ionizer is doing. Keep it between 0.2 and 0.4 ppm, measured with a copper test kit. Test it every day or two after a refill until copper reads 0.2 ppm, then every week until two readings in a row are between 0.2 and 0.4 ppm, then every two weeks. ClearBlue’s manual asks for the two-weekly test; the weekly test until the setting holds is ours.
• The controller has two settings. Maintain is the everyday output, a number from 0 to 99. Increase runs the cell at full output for the number of hours you set, up to 99, and then drops back to Maintain. ClearBlue’s manual sets the starting number from the tub’s volume as a share of the model’s maximum: Maintain = litres ÷ 9,500 × 33, rounded to a whole number, with Increase set to the same number of hours. The figures 9,500 and 33 are from page 8 of ClearBlue’s 2021 manual; the 2026 manual carries the same calculation on its page 8, so check them against your copy. For our 6 ft × 4 ft tub, 2,327 L, that is 8; the online version of this manual works it out in the “Your tub” box. Treat these numbers as a starting point only: raise Maintain if copper stays under 0.2 ppm, and lower it if copper goes over 0.4 ppm.
• On a fresh fill, copper starts at zero and takes days to come up. Use Increase after every refill, and test copper on the schedule above. ClearBlue says not to reduce chlorine until copper reaches 0.2 ppm, and gives 3 to 5 ppm for a spa until then. So on a fresh fill, use the higher level in Section 02 (stay out below 3 ppm, dose to 4 ppm) until copper reads 0.2 ppm, then go back to your usual level. Section 10 repeats this with the doses.
• If copper reads above 0.5 ppm, stop the ionizer (set Maintain to 0) and drain part of the water (Section 10). A partial drain is not a fresh fill: keep your usual chlorine level. Start the ionizer again, at a lower Maintain number, once copper is under 0.4 ppm.
• The Mineral Action light is lit or flashes blue while the cell is putting out minerals. At a low Maintain number it is on for only part of each hour, so watch for a full hour before deciding the unit is not working. A red flashing light means the cell is not plugged in fully. If the light never comes on, see ClearBlue’s manual or contact us.
• ClearBlue asks for dissolved solids of at least 500 ppm. Very soft or filtered fill water can be under that, and the ionizer will not run until it is corrected. Balance the water first; the balancers raise dissolved solids and are often enough. If the light still does not come on, ClearBlue’s manual says to add about 130 g (half a cup) of plain, non-iodized salt every 10 minutes until it does. Ask us before you do it the first time.
• ClearBlue asks for alkalinity of 80 to 120 ppm, pH of 7.2 to 7.6 and calcium hardness of 200 ppm or more. The ranges in Section 02 meet all three.
• ClearBlue’s manual gives a stabilizer range of 30 to 50 ppm and says to change to unstabilized chlorine above 50 ppm. This manual does not use unstabilized chlorine on cedar. So a ClearBlue tub is drained at 50 ppm, not 80. Use the 50 ppm figure in the “Your tub” box in Read This First, and the 50 ppm column in Appendix B. The dichlor total at 50 ppm is 98 g of 56% for every 1,000 L, or 88 g of 62%. In our 6 ft × 4 ft tub that is 228 g or 206 g. Below 30 ppm is fine; never add stabilizer to reach it. A new ClearBlue tub dosed twice a day at the higher level can reach 50 ppm within a week or two; that drain counts as one of the early drains in Section 01. High stabilizer together with copper may also leave a purple deposit.
• The cell wears away and has to be replaced. ClearBlue says to check it every six months in a hot tub, with the power off, and to scrape off any scale on the electrodes. Replace the cell when the electrodes are worn to 10 mm (half an inch) or less. ClearBlue gives two to three years in a hot tub, without guaranteeing it. A drain is a good time to look.
• Keep the controller out of rain and direct sun. It has no parts for you to service. Repairs go to ClearBlue.

Older ClearBlue units

Tubs fitted before the CBI-350 series have the ClearBlue model A-400, with the 2016 manual. The model is on the back of the controller. Everything above applies to it, except that the 2016 manual gives the electrodes about a year (2,160 hours on) and says to check them once a season; check them at every drain. Its settings are from its own table, not the formula above: for example, Ion/Action 18 and Large Dose 20 hours for 1,900 L. Apart from that, only the names on the controller differ. We do not fit an ionizer with an internal wood stove (Section 02); if your tub has both, contact us before the next fill.

• Ion/Action is what the 2026 manual calls Maintain: the percentage of each hour the cell is on.
• Large Dose is what the 2026 manual calls Increase, with one trap: Large Dose defaults to 24 hours, and the 2016 manual’s own table gives about 20 hours for a tub of 1,900 L, so set the hours from that table rather than running the default.
• The Ionizing light is the Mineral Action light. The 2016 manual does not describe a red light or a low-solids mode; if the light will not come on, see the salt note above and contact us.

The 2016 manual’s chlorine range stops at 3 ppm, so the higher level’s 4 ppm target is above it, as it is above the heater makers’ ranges (Section 02).

Clear Comfort CCW25

Clear Comfort describes the CCW25 as an oxidation system. Air is drawn through a cartridge in the unit and fed into the plumbing, where it oxidizes contaminants as the water goes past.

Clear Comfort’s water care page for spas gives 0.5 to 3 ppm of chlorine. As with the ClearBlue, that is the range for running the equipment, not a water safety range. This manual’s minimum and target apply with the CCW25 fitted.

• The green light on the control unit should be on whenever the pump is running, and Clear Comfort says the unit should run only then. If the light is off with the pump on, or on with the pump off, contact us.
• The CCW25 treats the water only while water is moving. Our 12-hour minimum (Section 09) is also Clear Comfort’s; they prefer 24.
• The air flow meter should read between 0.5 and 2 L/min. Adjust it with the dial on the meter. A dirty cartridge in the tub’s filter cuts the air flow, so keep the cartridge clean.
• Keep calcium hardness at 250 ppm or lower.
• MPS is not a weekly dose on a CCW25 tub: use it after heavy use, or when the water looks dull or smells (Section 06).
• Clear Comfort’s instructions call for a chlorine shock on every fresh fill. In a cedar tub, use the fresh-fill dose in Section 10 and no more.
• Replace the CCW25 cartridge once a year, whatever the light shows: it counts running hours, and at 12 hours a day it is still green at one year. Before you touch the unit, switch the tub off at the breaker and wait until every light on the unit is out. Never work on it while it is wet. Follow the instructions with the new cartridge; nothing is sent back.

Balancing and Dosing

Balance the water in the same order every time, because each adjustment moves the next reading: alkalinity first, then pH, then calcium, then chlorine. Make one adjustment, let the water circulate for 30 minutes, test again, and then move on. Nobody gets in for 20 minutes after any product, as in Section 04.

Know your tub’s volume

Every dose depends on how much water the tub holds. The volume is on the drawing or specification sheet for your tub; if you do not have it, ask us before you dose. The examples in this manual are for our 6 ft × 4 ft tub, 2,327 L (615 US gal). Appendix B has the figures for other tubs. Write yours in the box in Read This First.

Dosing rates

Check each label against the strength shown here. Appendix B covers dichlor of any strength; for the other products, ask us if yours differs.

For example, that tub with alkalinity at 70 ppm, aiming for 110 ppm, needs about 156 g of sodium bicarbonate. Dissolve a large dose like that in two or three lots.

Weigh your doses. A spoonful of one product does not weigh the same as a spoonful of another. Use a different cup from the one kept for dichlor, and rinse and dry it between products.

When pH is low

Low pH usually means low alkalinity, especially in a new tub. Bring alkalinity into range first and test again. If pH is still under 7.2 and your tub has jets, run them with the air controls open for 30 minutes and test again. Aeration raises pH without adding anything. If that is not enough, or the tub has no jets, use a pH increaser (sodium carbonate, also called soda ash) at the rate on its label, in small steps. We give no figure for it because it raises alkalinity as well; add a little, circulate 30 minutes and test both.

When pH is above 7.6 or alkalinity above 120

Once a tub is past its first months, jets and air push pH up. Bring it down with pH decreaser (sodium bisulfate), a little at a time: no more than 6.5 g per 1,000 L at once, which is 15 g in our 6 ft × 4 ft tub. Then circulate for 30 minutes and test again. If the label gives a smaller dose, use the label’s. Keep the air controls closed between soaks.

pH decreaser lowers alkalinity as well, by about 10 ppm for every 26 g per 1,000 L. If alkalinity is above 120 ppm, lower it the same way, one small dose at a time. Stop when pH reaches 7.4, let pH come back up, and repeat until alkalinity is in range. Running the jets with the air controls open brings pH back up sooner.

When calcium is high

Calcium only comes down by dilution. Drain part of the water and refill (Section 10). If your fill water itself tests over 250 ppm, dilution will not help: call us before you refill.

Adding chemicals

• Dissolve every product in a bucket of tub water first, and pour it in with the pump running. On a tub without jets, stir the water after pouring, as you do with chlorine (Section 04).
• Add the product to the water, never water to the product.
• Use one product per bucket, and rinse the bucket before the next one.
• Calcium chloride gets hot as it dissolves. Add it to the bucket slowly, no more than 300 g per bucket whatever the size of the tub, and leave an hour between buckets. Each bucket is one adjustment: test before the next.

Other products

Spa enzyme products break down body oils and lotion so that they clear faster and leave less of a scum line. They are optional. They are not a sanitizer, and they do not replace the chlorine dose or the weekly MPS. If you use one, choose a product whose only active ingredient is enzymes, with no clarifier, sequestering agent or fragrance. Add it at the label rate, and not on the same day as MPS. The labels we have seen say not to use them with or soon after a shock, and MPS counts. Stop if the water foams. On a ClearBlue tub, check with ClearBlue first. We have not tested enzyme products on cedar.

The floating sponges sold for soaking up body oil are harmless. They add nothing to the water and pick up some of what would otherwise end up on the scum line. If you use one, rinse it every week, replace it when it stops absorbing, and lift it out before a plumbing flush.

Ask us before adding anything else, including clarifiers, defoamers, stain-and-scale products, algaecides, fragrances, bath salts and oils. We do not recommend them for cedar, and some interfere with the ClearBlue. The case we are most likely to agree to is a sequestering agent on a tub without a ClearBlue whose fill water carries iron that the pre-filter does not catch (Section 12); we will tell you which product and how much, because we do not know what every sequestering product does to the surface of the wood over time.

The Routine

This is the routine in outline. The sections it points to have the detail and the limits. Once a tub is past its first months the weekly work is short, on top of a test before and after each soak.

Circulation and the filter

• Water has to pass through the filter every day. Leave the tub powered, with filtration running at least 12 hours a day. That is our minimum for every tub. A Gecko electric system leaves us set to filter 24 hours a day; a gas, propane or heat-pump system is programmed at installation, so ask the installer what was set. You can shorten a schedule down to 12 hours. After a keypad reset or a power cut, check that the schedule is still there.
• Rinsing a filter cartridge means hosing it off. Cleaning it means soaking it in cartridge cleaner, which takes hours. Keep a second cartridge so that a clean one is ready at each drain.
• Rinse the cartridge whenever flow drops, and at least once a month. In a new tub’s first month, rinse it every week.
• Replace a cartridge when the pleats are flattened or torn, or when it no longer rinses clean. Never run the pump with the cartridge out.
• On an electrically heated tub, jetted or circulation-only, the cartridge is a 50 sq ft Waterway 817-5000. Gas-heated and heat-pump tubs have a larger filter: a 100 sq ft Jandy CS100 (cartridge R0462200) or 200 sq ft CS200 (R0462400), or a 100 sq ft Hayward C100S (cartridge CX100XRE) or 200 sq ft C200S (CX200XRE). The filter model is on the filter body and the part number on the cartridge: check them before ordering, and keep the spare in its box with the log.

When you are away

• Before you leave, test, balance, dose to your target and close the cover. Dose MPS before you go if the weekly dose is due within the next few days, and rinse the filter cartridge. Leave the power on and filtration running.
• For an absence of more than a week, turn the temperature down as far as the control allows. On a Gecko in.k500 keypad, lower the set point and leave the mode on Standard: Away and the energy-saving modes also cut filtration. On an in.k300, lower the set point and leave economy mode off. Switch a gas heater or heat pump off at its own control. A wood-fired tub simply stands cold. The pump and the filtration schedule stay on: still water in the pipes is where biofilm grows, and circulation is part of the freeze protection. In freezing weather, follow the equipment manual.
• If someone can test and dose three times a week while you are gone, have them do it. Make sure it is an adult who has gone through Read This First and Section 04. Once a week is enough for a tub nobody is using; see “Second homes”, later in this section.
• With a new tub that does not yet hold chlorine overnight, have that person test and dose every day, or plan to drain and refill when you return.
• When you get back, test before anyone gets in. On an electric heater, turn the heat up as you arrive; on a gas heater or heat pump, test and balance first, then switch it back on (Section 02). If chlorine reads zero and it is more than three days since chlorine was last in the water, keep everyone out and follow Section 11; after more than a few days away, expect that. Within three days, dose to your target (Section 04).
• Do not leave the tub empty while you are away (Section 10).

Second homes

A tub that stands between visits needs someone to keep chlorine in it. Dichlor cannot be fed automatically, and the feeders that run unattended (chlorine pucks, liquid chlorine systems and bromine floaters) are not for cedar. A ClearBlue or CCW25 keeps working between visits, but chlorine still has to be kept in the water. Plan for one of these.

• With a caretaker or pool service. Give them this manual, and have them keep to it: test and dose to your target at least once a week, treat a zero reading as Section 11 says, and never chlorine-shock the tub, add pucks or use bromine (MPS at the manual’s rate is the only shock allowed). Weekly visits are further apart than the three days between tests in Section 03, and we accept that for a tub nobody is using. A restart needs a visit the next day, so if they cannot come back, a zero reading means a flush, drain and refill instead. Have them log every visit. Give them the quick reference sheet (WC-01-S), from forestcooperage.com/water-care or from us, with the box at the top filled in for your tub.
• Without one, visits two weeks apart or less. Dose to your target and close the cover when you leave. On arrival, test before anyone gets in. If chlorine reads zero and it is more than three days since your last dose, follow Section 11: nobody gets in for an hour and until the soak checks (Section 04) pass, and the next morning’s test tells you whether the fill is worth keeping. Within three days of a dose, dose to your target (Section 04). If it reads above zero, dose to your target and run the soak checks (Section 04). If anyone in the household is in a higher-risk group, the restart is not open to you (Section 11): flush, drain and refill on arrival, or arrange a caretaker.
• Without one, visits more than two weeks apart. Flush, drain and refill on arrival (Section 10), every time; the six-week flush exception does not apply. In freezing weather, ask us before you drain. Never leave the tub dry between visits. If your stay is shorter than the three fresh-fill days, test each day you are there and dose to your target before you leave. Allow most of a day for an electric heater to bring a cold 6 ft × 4 ft tub up to temperature, longer for a bigger tub; gas is faster.

In every case, turn the heat down and leave the power and the filtration schedule on. Winter shutdown and freeze protection are outside this manual; ask us.

Drain and Refill

Some things only leave the tub when the water does: stabilizer, dissolved solids and what people leave behind. Draining on schedule is as much a part of water care as the chlorine.

When to drain

• Stabilizer reaches your drain point, or the running total of dichlor reaches the total for that point. The drain point is 80 ppm (Section 05), or 50 ppm for a tub with a ClearBlue ionizer (Section 07). Drain before the next soak if you can, and within a week at the latest. This is usually what sets the schedule.
• Total dissolved solids reach 2,000 ppm.
• The walls feel slimy or the water smells bad. Do not try to save that water.
• The water is cloudy and has not cleared within a day or two of following Section 12.
• Four months have passed, whatever the readings.
• On a new tub: one to two weeks after the first fill, and again about one month after the first fill.

Health Canada’s model label for spa chlorine gives a drain interval of its own. The number of days between drains is the volume of the tub in litres, divided by ten times the largest number of people who use it in a day. For our 6 ft × 4 ft tub, drawn for six people, that is 2,327 ÷ 60, or 38 days; with four people it is 2,327 ÷ 40, or 58 days. Count the busiest day, not the average. Your own label may not print the formula. If the label on your chlorine gives a shorter interval than the list above, follow the label.

Where the water goes

Ask your municipality or regional district where hot tub water may go before you drain. Do not assume it can go on the ground or down a storm drain. Draining to a storm drain, ditch, stream, lake or shoreline is commonly forbidden. If you will drain within a day of the last soak, skip the chlorine dose after that soak so that the level is low when the water leaves. Read the flush product’s label for disposal as well. Do not send a full tub into a septic system without asking whoever services it. Water from a ClearBlue tub contains copper, which is toxic to fish and other aquatic life, and must never reach a storm drain or natural water.

The plumbing flush

Biofilm, a slimy layer of bacteria that chlorine does not reach well, builds up inside the pipes. A plumbing flush made for spas, often sold as a purge, loosens it so that it leaves with the old water. We use Ahh-Some; any other spa flush, at its label rate, does the same job. Flush at every drain, with two exceptions. A new tub’s two early drains (Section 01) do not need it unless the water is cloudy, smells or feels slimy. After that, skip the flush when less than six weeks have passed since the last one and the water is clear and holds chlorine overnight, as on a tub that is drained often because it is used every day. Any drain caused by a problem gets the flush, however recent the last one.

Procedure

1. Flush the plumbing, with the old water still in the tub, if the rules above call for it. Run the pump, and the jets with the air controls open if your tub has them, for as long as the label says. A tub without jets flushes more slowly, so give it the longest time the label allows. Foam and dirt coming up are normal. If the foam is thick and dirty, drain, refill and flush a second time before the final drain. Keep everyone out once the product is in, and keep your face away from the water while it runs. Never add bleach, even if the label offers it, and do not use the product as a cleaner on the wood.
2. Turn the temperature down and let the pump run for a few minutes. Then switch off the heater and the pump at the breaker. With a gas heater or heat pump, switch it off at its own control as well, before the water drops below the suction fittings, the grated fittings low on the wall where water leaves the tub. On a wood-fired tub, let the fire go out and the stove cool before the level drops (Section 02).
3. Drain the tub and the equipment completely. If you are not sure how to drain your tub, ask us.
4. Wipe the sticky residue from the flush off the wood, then wipe down the whole inside with fresh water and a soft cloth. Use a soft brush where there is film. Rinse the tub with fresh water before you refill, so that none of the purge product is left on the cedar. No detergents, no household cleaners and no pressure washer. The floor is slippery, so use a step and have someone nearby.
5. Put in the clean spare filter cartridge, and clean the one you took out.
6. Close the drain and check that the filter lid is tight. Our electric skids have two suction valves ahead of the filter: both must be open before the pump runs. On other skids, open every valve you closed to drain or to change the cartridge, except a heater bypass, which stays open until the water is balanced (Section 02).
7. Refill straight away to the operating level, about 15 cm (6 inches) below the rim. A pre-filter on the end of the hose takes out sediment and some of the iron, copper and other metals in the fill water. Use one on every fill on well water or any supply that has ever left a stain, and replace it when the flow drops; ClearBlue recommends one on every tub. Iron matters more in cedar than in acrylic: besides its orange mark, it reacts with the tannins in the wood to leave a dark stain. The pre-filter does not soften the water much, so test calcium after filling as usual.
8. Turn the power back on and check that water is circulating: the jets or the return fitting should show flow within a minute. If not, switch off at the breaker at once, so the pump does not run dry, and look for a closed valve or an airlock before you call us or open the equipment manual. Leave a gas heater or heat pump switched off at its own control for now.
9. Balance alkalinity, then pH, then calcium (Section 08). Switch a gas heater or heat pump on only when all three are in range.
10. Give the first chlorine dose (see below), with the cover off for 20 minutes as usual.
11. Put the cover on and heat the water. Test again once it is up to temperature.

The first fill

The first fill follows the steps above from step 6, with these differences. Appendix B lists what to have on hand before you start. If we or an installer do the first fill, ask them for the readings and the doses for your log; the new-tub routine starts from that day whoever did the fill.

• Test the fill water before you balance. If calcium is over 250 ppm or alkalinity over 120 ppm, or it is well water, call us first.
• An electric heater can run while you balance. A gas heater or heat pump stays off until alkalinity, pH and calcium are in range. Alkalinity and pH are not optional on the first fill: new cedar pulls both down, and water below 7.2 corrodes heaters. Calcium is different. Its job is to protect metal, and only the gas heaters, the heat pump and the ClearBlue specify a minimum, so on an electric tub with no ClearBlue you can leave calcium until the fill after the early drains.
• Balance in order, 30 minutes apart, then give the first chlorine dose (below) and write everything in the log. On a ClearBlue tub, set Increase (Section 07).
• The first soak can happen as soon as the water is up to temperature; with an electric heater that is usually the day after the fill. Dose just before the soak, wait 20 minutes, test, and get in only if the tub passes the soak checks (Section 04). That dose and the fresh-fill dose count as the two doses a new tub gets in a day; the new-tub rules in Sections 01 and 04 apply from the first day.

Chlorine on a fresh fill

New water has no stabilizer in it, so chlorine is at its strongest on a fresh fill. Do not chlorine-shock it, whatever the label or a pool shop says. Dose to your target as on any other day, and test every day for the first three days.

• The first dose in our 6 ft × 4 ft tub is 12 g of 56% dichlor or 11 g of 62% for a 3 ppm target, and 17 g or 15 g for a 4 ppm target.
• On a ClearBlue tub, use the higher level (stay out below 3 ppm, dose to 4 ppm) until copper reads 0.2 ppm, then go back to your usual level (Section 07). The first dose is then the 4 ppm one.
• For the first three days, dose to your target whenever the daily test is below your minimum, except on a day you plan to soak, when the dose before the soak is the one that counts (Section 04).
• Run the soak checks (Section 04) before every soak during these days, as on any other day.

Once a tub is past its first months, a fresh fill usually holds a reading overnight after one or two doses. If it reads under 1 ppm the morning after each of the first two doses, something is using up the chlorine. Keep everyone out, flush the plumbing, drain, put in the clean spare cartridge and refill. If the next fill does the same, contact us.

A new tub may not hold a reading overnight at all. Section 01 covers that.

Draining part of the water

Too much chlorine, copper or calcium is brought down by dilution.

1. Switch the heater and the pump off at the breaker. Switch a gas heater or heat pump off at its own control as well. On a wood-fired tub, let the fire go out and the stove cool first, and do not drain below the top of the stove.
2. Drain a third to a half of the water, or down to the top of a wood stove, whichever is less. Keep strongly chlorinated water away from plants, storm drains and natural water.
3. Refill to the operating level, switch the pump back on and circulate for 20 minutes. Leave a gas heater or heat pump off.
4. Test for whatever you drained to bring down; for chlorine, use the diluted test if the level may still be high (Section 03). Repeat if it is still too high.
5. Test pH, alkalinity and calcium and rebalance (Section 08). Switch a gas heater or heat pump back on only when all three are in range.
6. Reduce the dichlor running total in proportion to the water you took out (a third out: total × 2/3), and write it in the log, or leave it and drain early (Section 05).

Recovery

Three situations need more than the routine: a tub that has gone without chlorine, a tub that has had too much, and wood that has been bleached.

A tub that has gone without chlorine

This means a tub that reads zero when it is more than three days since chlorine was last in the water (the last dose or the last test that showed any, whichever is later), or when you do not know how long it has been.

Public health guidance for disinfecting a hot tub calls for chlorine far above the 5 ppm limit in this manual. A cedar tub cannot take that, so the restart below uses far less chlorine than the guidance calls for. It gets chlorine back into the water. It does not disinfect the tub or the pipes.

Do not try to restart if any of these is true. Flush the plumbing, drain, wipe down and refill instead (Section 10). A new tub skips the flush unless its water is cloudy, smells or feels slimy: drain and refill, which it was due for within a week or two anyway.

• The water is cloudy, smells bad or leaves a slimy film on the wood.
• It is more than two weeks since chlorine was last in the water, or you do not know how long.
• Anyone who uses the tub is in the higher-risk groups listed in Read This First.
• The tub is new and does not yet hold chlorine overnight (Section 01).
• Nobody can test the water the next day.

Otherwise:

1. Balance alkalinity and pH.
2. Add dissolved dichlor once, enough to bring chlorine to 4 ppm. In our 6 ft × 4 ft tub that is 17 g of 56% dichlor or 15 g of 62%. That is the “target 4 ppm, reading 0” dose in Section 04. Keep everyone out for an hour with the pump running: long enough for a drop test to show whether the water is using the chlorine up fast. After that, the soak checks in Section 04 decide: if the water is clear and chlorine is at or above your minimum, it can be used that evening.
3. Test again the next morning, whether or not anyone soaked. If chlorine is at 1 ppm or more (use the drop kit if a strip shows the 1 block), we treat the restart as having held. Go back to the routine, and the soak checks apply as usual. That day, dose MPS and rinse the filter cartridge.
4. If the reading is under 1 ppm but the water is clear, has no smell and the walls are not slimy, dose once more, to your target this time. The same one-hour wait and soak checks apply, and test again the next morning.
5. If that reading is under 1 ppm as well, stop dosing. Two doses that will not hold mean something in the tub is using up chlorine faster than dosing can replace it. Flush the plumbing, drain, wipe down and refill (Section 10).

Too much sanitizer

The usual cause is a mix-up, such as a balancer-sized scoop of chlorine, a dose meant for a bigger tub or a second dose added because the first test read low. Deal with it the same day. The sooner the level comes down, the less chance of damage to the wood.

• Keep everyone out until free chlorine is 5 ppm or lower. If anyone who was in the tub has sore eyes or skin, rinse with fresh water. If anyone has trouble breathing, get them into fresh air and call emergency services. Then follow the first aid directions on the chlorine label.
• A very high level can bleach the test so that it reads low. Use the diluted test (Section 03).
• Keep the pump running, except while you drain. If there are undissolved granules on the floor or seats, sweep them off the wood with a soft brush until they dissolve. Wear gloves and keep your face away from the water. Granules left sitting bleach the wood under them.
• Leave the cover off while you are with the tub, so that the chlorine can escape. Put it back on if you have to leave.
• Between 5 and 10 ppm, wait with the pump running and test again every few hours.
• Above 10 ppm, do not wait for it to fall: drain part of the water (Section 10), and repeat until it reads 5 ppm or lower.
• With a gas heater, heat pump or internal wood stove, drain part of the water at any reading above 5 ppm; switch a gas heater or heat pump off first. The exception: a high strip reading the day after MPS that followed a weighed chlorine dose; wait and test again (Section 06).
• A chlorine neutralizer (sodium thiosulfate) is an addition to the partial drain, not a replacement for it, and it can only be dosed once a test, diluted if need be, gives you a number. It brings the level down faster. Work out the amount on its label for the ppm you need to remove, add half of it, circulate for 30 minutes and test before adding more. Any excess stays in the water and uses up the next chlorine doses.

Once chlorine is 5 ppm or lower, rebalance pH, alkalinity and calcium. Nobody in until the tub passes the soak checks (Section 04); test again the next day.

Bleached or fuzzy wood

Wood that has had too much sanitizer goes pale, then white, and the surface fibres loosen into a soft fuzz that sheds into the water. Pale spots on the floor or a seat usually mean granules or a tablet sat there. Whitening over the whole interior points to one of three things: chlorine or bromine kept too high for too long, high pH, or a product this manual says not to use.

White or fuzzy wood means the water has been hard on the tub. Before anyone gets in, test chlorine with the diluted test (Section 03) and run the soak checks (Section 04). If the water passes, the wood alone is no reason to stay out.

• Test pH and stabilizer as well, and write the readings down. List every product that has been used on the tub.
• If chlorine is above 5 ppm or pH is above 7.8, correct that first.
• Stop whatever caused it. Go back to weighed doses, dissolved in a bucket and added only after a test.
• Rinse the filter cartridge more often while the wood is shedding fibres.
• Send us photographs and the log, and we will tell you where you stand. Do not sand, scrape or refinish before talking to us.

On a tub still on bromine, do the diluted test for bromine. Keep everyone out unless bromine is inside the range on its label, or at 8 ppm or lower if the label gives no top figure. Above that, drain and change to dichlor now (Appendix A); do not wait for it to fall.

The damage does not reverse; removing the cause is the only way to stop it spreading. The warranty does not cover damage caused by chemical imbalance.

Troubleshooting

Test before you look anything up here. Every remedy starts from a fresh test. If a reading is low or blank, check whether the diluted test in Section 03 applies before you add anything.

If the table does not solve a problem with the water, or the readings do not make sense, stop using the tub, photograph the test next to your log and contact us: support@forestcooperage.com, 1-877-557-1961 or (250) 642-4899, Monday to Friday, 8:00 a.m. to 4:30 p.m. Pacific time.

Changing from Bromine

We used to recommend brominating granules for our tubs. We now recommend dichlor for every tub. If your tub is on brominating granules, change over at your next drain and refill.

The granules we recommended (Health Canada registration number 27589) are a mix of sodium dichlor, the same chlorine this manual uses, and sodium bromide. The bromide turns the chlorine into bromine as it goes in, so the tub runs on bromine, and the stabilizer in the dichlor builds up in the water just as it does in Section 05. Changing to dichlor alone stops more bromide going in. The bromide already in the water stays until it is drained, and any oxidizer added to that water, chlorine or MPS, turns it back into bromine. That is what makes the level hard to control. Health Canada advises against bromine in any tub with an ionizer, ozone or UV system; we believe this is the reason.

Other bromine granules, sold under names such as BCDMH, are a different chemical; in August 2026 Health Canada proposed to cancel their pour-in granular form, with no final decision published when this manual was written. The changeover below applies to them in the same way.

The change cannot be made partway through a fill. The tub stays a bromine tub until the old water is gone. You can drain early to make the change.

Until you change over

• Follow the label on your brominating granules and test before every soak. Keep everyone out below the bottom of the label range and above the top of it, or above 8 ppm if the label gives no top figure.
• MPS (non-chlorine shock) turns the bromide in the water back into bromine, and a full dose can raise bromine sharply. Use it only as your bromine label directs, and test before anyone soaks.
• If your tub has a ClearBlue ionizer or a CCW25, change now. Health Canada’s page “Swimming pool and spa chemicals” says not to use sodium bromide or any bromine product with an ionizer, an ozone generator or a UV device; Clear Comfort says the same for the CCW25.

At the changeover drain

1. Flush the plumbing before you drain, as in Section 10. The pipes hold bromide water, so do not skip this.
2. Drain completely, including the equipment, then wipe down and rinse the wood as in Section 10. If you are not sure how to drain your tub, ask us.
3. Fit the clean spare cartridge or a new one, and clean the old one.
4. Take the brominating granules away from where you keep the tub chemicals. Dispose of what is left as the label directs.
5. Refill, balance and start the fresh-fill chlorine doses (Section 10).

The first fill on chlorine

Some bromide carries over in the plumbing and in the wood. It turns part of each chlorine dose into bromine, which still sanitizes and still shows on a chlorine test. Most of it should be gone after the next drain. No extra rinse fill is needed, and the tub should not be left empty to dry out.

Dosing Reference

The doses and limits from this manual in one place. Quantities in the first table are for our 6 ft × 4 ft tub, which holds 2,327 L (615 US gal).

Doses for our tubs

Volumes are from our drawings, with the water 15 cm (6 inches) below the rim. Round tubs are listed by diameter × height. Soaker volumes are approximate. All doses are in grams. The 4 ft tubs and the soakers have a circulation pump and no jets, so where this manual says to run the jets, stir the water instead (Section 04).

Doses by volume

For a tub that is not in the table above, every dose is in proportion to the volume. Per 1,000 L of water: dichlor 56%, 1.8 g per ppm (62%: 1.6 g); sodium bicarbonate, 17 g per 10 ppm of alkalinity; calcium chloride 94%, 12 g per 10 ppm (77% flake: 14 g); MPS 43–45%, 30 g upper limit; dichlor 56% total to the 80 ppm drain point, 156 g (62%: 141 g), and to 50 ppm, 98 g (62%: 88 g). Multiply by your volume in thousands of litres; US gallons × 3.785 = litres. For any other dichlor strength, grams per ppm = litres ÷ (10 × the available chlorine percentage). Example: 2,500 L, 56% dichlor, reading 1 ppm, target 3 ppm: 2.5 × 1.8 = 4.5 g per ppm, and you need 2 ppm, so add 9 g. If your volume is uncertain, round it down, never up.

What to keep with the tub

Products. Sodium dichlor granules, 56% or 62%; potassium monopersulfate (MPS); sodium bicarbonate (alkalinity increaser); sodium bisulfate (pH decreaser); sodium carbonate (pH increaser); calcium chloride (calcium increaser); a spa plumbing flush (we use Ahh-Some) and cartridge cleaner; chlorine neutralizer (sodium thiosulfate), for Section 11 only.

Tests and tools. Test strips, and a drop kit for free chlorine (DPD or FAS-DPD), pH, alkalinity and calcium, with a black-dot stabilizer test; a TDS meter; a copper test kit on a ClearBlue tub; distilled water for the diluted test; a digital scale reading to 0.1 g, kept for tub chemicals only; a plastic bucket, a dry cup for dichlor only, a second cup for the other products, and a labelled scoop per product; a spare filter cartridge; a hose-end pre-filter (Section 10); gloves, eye protection, a clean plastic paddle and a soft brush; and a thermometer, which a wood-fired tub cannot do without, having no thermostat.