Pool Chemical Calculator
Doses for the three adjustments every pool owner makes: total alkalinity with baking soda, pH with soda ash or muriatic acid, and stabilizer (cyanuric acid). For chlorine doses, use the dedicated chlorine calculator.
pH doses are approximations, the true amount depends on your total alkalinity, which buffers pH changes. Add no more than half the dose at once, circulate 30 minutes, and retest. Always add acid to water with the pump running; never mix chemicals directly.
The dosing factors this calculator uses
All factors are standard industry values, scaled linearly to your pool volume:
pH up: 6 oz soda ash raises pH about 0.1 per 10,000 gal
pH down: 10 fl oz muriatic acid (31.45%) lowers pH about 0.1 per 10,000 gal
CYA: 13 oz cyanuric acid raises CYA 10 ppm per 10,000 gal
The alkalinity and CYA factors are essentially exact, they are simple mass ratios. The pH factors are honest approximations: how far a dose of acid or soda ash moves pH depends on your total alkalinity, because alkalinity is a buffer that resists pH change. At TA 120 the same acid dose moves pH less than at TA 70. That is why every good pool guide says: dose half, circulate 30 minutes, retest.
Worked example: low alkalinity after heavy rain
Rain is slightly acidic and dilutes the pool, a week of storms commonly knocks TA from 90 down to 60 ppm in a 15,000 gallon pool. To restore it:
- Needed increase: 90 − 60 = 30 ppm
- Factor: 1.5 lbs per 10 ppm per 10,000 gal
- Dose: (30 / 10) x 1.5 x (15,000 / 10,000) = 6.75 lbs of baking soda
- Add 3.5 lbs, circulate an hour, retest, then add the rest if still low.
Why alkalinity comes first
Total alkalinity is the shock absorber of pool chemistry. With TA in the 80 to 120 ppm range, pH drifts slowly and predictably. With TA below 60, pH swings wildly with every rainstorm and swimmer; above 140, pH climbs relentlessly and acid demand goes up. Fix TA first and half of your pH problems disappear on their own. Then set pH, then stabilizer, and finally chlorine, in that order.
Handling notes
- Muriatic acid: add slowly to the deep end with the pump running, pour close to the water to avoid splashes, and never pre-mix with anything.
- Soda ash can cloud the water briefly; it clears with circulation.
- CYA dissolves slowly, add it via a sock hung in front of a return jet and give it up to a week before trusting the test reading.
- Store acid and chlorine physically apart; their fumes react.
Frequently asked questions
What order should I balance pool chemicals in?
Total alkalinity first, then pH, then stabilizer (CYA), then chlorine. Alkalinity is the buffer that holds pH steady, so adjusting pH before alkalinity means doing the work twice. Calcium hardness can be adjusted at any point.
What are the ideal pool chemistry levels?
Commonly recommended ranges: pH 7.4 to 7.6, total alkalinity 80 to 120 ppm, cyanuric acid 30 to 50 ppm (60 to 80 for salt water pools), calcium hardness 200 to 400 ppm, and free chlorine 1 to 4 ppm scaled to your CYA.
Can I use baking soda from the grocery store?
Yes. Pool 'alkalinity increaser' is sodium bicarbonate, chemically identical to grocery baking soda, usually at a higher price per pound. Buy whichever is cheaper per pound.
How much baking soda to raise alkalinity in a 15,000 gallon pool?
About 2.25 lbs of baking soda raises total alkalinity 10 ppm in 15,000 gallons. To go from 60 to 90 ppm you would add roughly 6.75 lbs, ideally split into two doses with a retest in between.
Why does my pH keep rising?
The most common causes are high total alkalinity outgassing carbon dioxide, water features and spillovers that aerate the water, fresh plaster curing (up to a year), and salt water generators, whose cells naturally drive pH upward. Persistent risers often benefit from running alkalinity at the lower end, around 70 to 80 ppm.