What order should I add pool chemicals in?

Adjust total alkalinity first, then pH, then calcium hardness, stabilizer and salt, and add chlorine last. Alkalinity buffers pH, so pH moves more predictably once alkalinity is right, and chlorine goes in last so it is not used up while the rest of the water is still being adjusted. Let each chemical circulate before adding the next.

What should my pool chemical levels be?

Typical targets for an outdoor chlorine pool are free chlorine 3 to 5 ppm, pH 7.4 to 7.6, total alkalinity 80 to 120 ppm, calcium hardness 200 to 400 ppm for plaster, and cyanuric acid 30 to 50 ppm. Salt pools usually run alkalinity lower, around 60 to 80 ppm, cyanuric acid higher, around 60 to 80 ppm, and salt at whatever the chlorine generator's manual asks for, usually 2,700 to 3,400 ppm.

Can I add pool chemicals at the same time?

No. Add one chemical at a time, in different parts of the pool, with the pump running, and give each one time to circulate before the next. Some combinations are dangerous: chlorine products and acid must never be mixed, and dry chlorine products must never be mixed with each other. Always add chemicals to water rather than water to chemicals.

Why does the calculator tell me to drain instead of adding something?

Calcium hardness, cyanuric acid and salt don't break down or get used up, and no pool chemical takes them out reliably. The only way to lower them is to replace some of the water with fresh water. The calculator shows the share of the water to replace, assuming the fill water has none of the reading in it.

How accurate is a pool chemical calculator?

The calculations are consistent, but the answer is only as accurate as the pool volume and the test results you enter. A volume that is 20% too high gives doses that are 20% too high. pH is the least predictable reading because borates, stabilizer and fresh plaster all buffer it. Add about three quarters of each dose, let it circulate, and re-test before adding the rest.

Do salt pools need different chemical levels?

Yes, slightly. A salt chlorine generator pushes pH up as it runs, and lower total alkalinity slows that rise, so salt pools usually run alkalinity around 60 to 80 ppm. They also run more stabilizer, around 60 to 80 ppm, so the chlorine the cell makes lasts longer in sunlight. Switch the calculator to Salt pool to start from those targets.

Free pool tool

Pool Chemical Calculator

Enter your test results and the levels you want, and this calculator works out every dose for your pool's volume, lists them in the order to add them, and shows the saturation index before and after.

Pool volume

gal

Not sure? Work out your pool volume.

Units

Pool type

ReadingCurrentTarget

Free chlorine(ppm)

Total alkalinity(ppm)

Calcium hardness(ppm)

Cyanuric acid(ppm)

Salt(ppm)

Leave a row empty to skip it. Targets are typical starting points; adjust them for your surface and equipment.

Water temperature

°F

Used for the saturation index.

Chlorine

Acid

Calcium

What to add, in order

01Total alkalinity
130 → 90
1.2 galMuriatic acid (31.45%)
- Acid lowers pH along with alkalinity. Lower alkalinity first, let it circulate, then re-test pH before the next step.
- Pour it slowly into the deep end in front of a return with the pump running. Always add acid to water, never water to acid.
02pH
7.9 → 7.5
Re-test before adding anything
- The acid in the alkalinity step lowers pH as well, usually below 7.5, so don't add more acid yet. Re-test pH once it has circulated.
- If pH ends up too low, aerate the water by pointing the returns up or running a water feature. That raises pH without bringing alkalinity back up. If it is still too high, use the muriatic acid calculator for the remaining drop.
03Calcium hardness
220 → 300
14.7 lbCalcium chloride (77%)
- Calcium chloride heats up as it dissolves. Pre-dissolve it in a bucket of pool water and add it slowly.
04Cyanuric acid (stabilizer)
30 → 40
1.25 lbCyanuric acid (stabilizer)
- Stabilizer dissolves slowly. Put it in a sock in front of a return or in the skimmer basket, and give it about a week before re-testing.
05Free chlorine
2 → 4
38 fl ozLiquid chlorine (12.5%)
- Adds nothing but chlorine and a little salt. It loses strength in the heat, so a jug that has sat in the sun may be weaker than its label.

Saturation index now

+0.45

Slightly scaling

After these doses

0.00

Balanced

Add about three quarters of the dose, let the pump circulate for an hour, and re-test before adding the rest. Never mix chemicals together, and always add chemicals to water rather than water to chemicals. Add each chemical separately and let it circulate before the next one.

How it works

Balance the Water in the Right Order

The calculator works through the readings in the order a technician adjusts them: total alkalinity, then pH, calcium hardness, cyanuric acid, salt, and free chlorine last. The order matters because the readings affect each other. Alkalinity is the water's buffer against pH change, so the amount of acid or soda ash it takes to move pH depends on how much alkalinity is there. Chlorine goes last because it is the reading that changes fastest, and adding it first would waste some of it while the rest of the water is still being adjusted.

Each step uses the water as the earlier steps leave it. The pH dose is sized on the alkalinity the alkalinity step leaves behind, not on the starting reading, because higher alkalinity takes more acid to move pH by the same amount. The chlorine step also reports what the product adds besides chlorine: dichlor and trichlor raise cyanuric acid, and cal-hypo raises calcium hardness, so the calculator counts that against your targets.

When you lower alkalinity with acid, pH falls at the same time, often further than you wanted, so the calculator doesn't stack a second acid dose on top for pH. It asks you to re-test pH once the alkalinity dose has circulated. If pH has dropped below your target by then, aeration brings it back up without raising alkalinity again.

Target levels

Typical Targets for Chlorine and Salt Pools

The calculator starts from the targets below and switches between them when you choose a chlorine pool or a salt pool. They are starting points for an outdoor plaster pool, so adjust them for your surface and equipment.

Reading	Chlorine pool	Salt pool
Free chlorine	3–5 ppm	3–5 ppm
pH	7.4–7.6	7.4–7.6
Total alkalinity	80–120 ppm	60–80 ppm
Calcium hardness	200–400 ppm	200–400 ppm
Cyanuric acid	30–50 ppm	60–80 ppm
Salt	—	2,700–3,400 ppm

Salt pools run lower alkalinity because the generator pushes pH up as it works, and lower alkalinity slows that rise. They run more stabilizer because the cell makes chlorine all day and cyanuric acid protects it from sunlight. The right salt level is whatever the cell's manual says. Vinyl and fibreglass pools can run lower calcium than plaster, so follow the manufacturer's guidance for those.

Worked example

A 20,000-Gallon Chlorine Pool at 82°F

Say the test reads free chlorine 1 ppm, pH 7.8, total alkalinity 70, calcium hardness 220 and cyanuric acid 30, and the targets are 4, 7.5, 90, 300 and 40. With 12.5% liquid chlorine, 31.45% muriatic acid and 77% calcium chloride, the calculator lists:

1. Total alkalinity	70 → 90 ppm	5.6 lb baking soda
2. pH	7.8 → 7.5	18 fl oz muriatic acid
3. Calcium hardness	220 → 300 ppm	19.6 lb calcium chloride
4. Cyanuric acid	30 → 40 ppm	1.66 lb stabilizer
5. Free chlorine	1 → 4 ppm	61 fl oz liquid chlorine

The pH dose is sized on the 90 ppm of alkalinity the first step leaves. Sized on the starting 70 ppm it would have been 14 fl oz, which would leave pH short of the target. The acid also takes about 3 ppm off the alkalinity. The saturation index starts at +0.05 and finishes at −0.02, so the water stays balanced throughout.

If you don't know the pool's volume, the pool volume calculator works it out from the shape and depth, and every calculator on this site remembers it.

The limits

What Only Comes Down by Draining

Calcium hardness, cyanuric acid and salt don't evaporate, break down or get used up, so they only ever climb. When one of them is above its target, the calculator shows the share of the water to replace instead of a product to add:

Share to replace = (current − target) ÷ (current − fill water level)

Bringing cyanuric acid from 100 ppm down to 50 ppm with fill water that has none means replacing half the pool. Test the tap water first if your area has hard water, because calcium in the fill water means more draining to reach the same target.

The dosing rates for pH, alkalinity, calcium and stabilizer are the ones the Pool Runs technician app uses, calibrated against the Orenda calculator and the PHTA alkalinity fact sheet. Chlorine and salt doses come straight from molecular weights. In our tests the pH doses land within about 6% of TroubleFreePool's Pool Math, and the alkalinity doses match the chemistry exactly.

For pool service companies

The same maths runs at every stop in Pool Runs

These calculators use the dosing and saturation-index formulas built into the Pool Runs technician app. A tech logs the readings at the pool, the app works out the doses for that pool's own volume, and the visit lands in the customer's service history and report without anyone typing it up later.

Readings and doses saved against each pool, with the saturation index for every visit
A mobile app that works offline in a backyard with no signal
Chemicals and parts tracked on every truck and in the shop

See the technician app

Try Pool Runs free

Free for 30 days, month to month, with white-glove onboarding to move your customers in.

Questions