Calculator
Pool pH calculator
Enter your pool gallons, current pH, and target pH. The calculator shows the exact dose for each common chemical to get you there — muriatic acid (31.45% or 14.5%), dry acid, soda ash, or borax. Math sourced from Trouble Free Pool / Taylor verified formulas.
| Chemical | Dose |
|---|---|
Muriatic acid (31.45%) Pour into deepest end with pump running; do not aerate. | 48 oz |
Safe acid (14.5%) | 104 oz |
Dry acid Adds sulfate — avoid for SWG pools (corrodes cell long-term). | 72 oz |
Pour acid slowly with pump running into the deep end. Never combine acid and chlorine in the same skimmer or bucket — chlorine gas. Re-test pH 30 minutes after dosing.
Pro tip — let AI handle multi-step
When pH and TA are both off (pH 8.2 + TA 130 is common in SWG pools), you don’t want to dose acid blindly — you want a multi-day aeration protocol that drops TA without crashing pH below 7.0. PoolAssist AI chat writes those protocols when you describe your readings.
How pH dosing math works
pH adjustment is non-linear because Total Alkalinity (TA) buffers the change. The formulas below assume TA in the normal range (60-120 ppm) and a single 0.2 pH delta per dose. If you need a bigger drop, split it into 2-3 doses.
To lower pH 0.2 (per 10,000 gal):
- Muriatic acid 31.45%: 12 oz
- Muriatic acid 14.5% (“safe acid”): 26 oz
- Dry acid / sodium bisulfate: 18 oz — avoid for SWG pools
To raise pH 0.2 (per 10,000 gal):
- Soda ash / sodium carbonate: 6 oz
- Borax: 11 oz — also adds borate buffer
Safety
- Never combine acid and chlorine. Wait at least 30 minutes between additions. Mixing produces chlorine gas.
- Pour acid into water, never water into acid. Always with the pump running, into the deep end, slowly.
- Wear eye protection + gloves. Even diluted muriatic acid splashes can damage eyes and stain clothing.
- Don’t add over the heater intake. Acid + hot heat exchanger metal = corrosion. Pour at the deep end with flow toward the skimmer.
FAQ
What's the ideal pool pH?
7.4 to 7.8, with 7.6 the sweet spot. Below 7.2 water becomes corrosive (eats grout, gaskets, pump seals); above 7.8 chlorine effectiveness drops sharply (a 7.5 pH pool needs ~30% less chlorine than a 7.9 pool to maintain the same kill power). For a gas-heated pool keep pH 7.4-7.6 specifically — heat exchangers scale fast above 7.6 with high TA.
Muriatic acid vs dry acid — which should I use?
Muriatic acid 31.45% (hydrochloric acid) is the workhorse: cheap, fast, no side products beyond a tiny chloride bump. Dry acid (sodium bisulfate, also sold as 'pH minus' or 'pH down') is safer to handle — no fumes, dry powder — but adds sulfate to the water. For SWG (saltwater) pools, AVOID dry acid: sulfate corrodes the salt cell over time. Stick to muriatic acid 31.45% for SWG pools.
How much does pH change when I add the recommended dose?
The calculator targets a fixed delta of 0.2 pH units per round. Larger drops in a single round can crash pH below 7.0 because pH dosing is non-linear (TA buffers it). For drops bigger than 0.4 pH units, do it in 2-3 rounds with a few hours between, retesting each round. The aerated 'aerate to raise pH while leaving TA low' trick works the other direction.
My pH keeps creeping up — why?
Outdoor pools naturally drift pH upward over weeks because dissolved CO2 outgasses (reverse of carbonated soda losing fizz). High TA accelerates this — TA above 100 ppm with a SWG can push pH up 0.2-0.4 per week. Two fixes: (1) lower TA to 60-80 ppm using muriatic acid + aeration, (2) accept the drift and dose acid weekly. Indoor pools rarely have this issue.
Can I add muriatic acid and chlorine the same day?
Yes, but NOT at the same time and NOT in the same skimmer. Wait at least 30 minutes between additions and pour them in different parts of the pool. Mixing concentrated acid with concentrated chlorine releases chlorine gas — extremely dangerous. As long as both are diluted in pool water at separate times you're fine.
Why does the calculator suggest different doses for the same target?
Different chemicals have different per-gallon ppm-shift ratios. Muriatic acid 31.45% drops pH 0.2 with 12 oz per 10K gal; dry acid (sodium bisulfate) needs 18 oz for the same drop because it's a weaker acid. Same target, different molarity = different dose. The calculator shows all options so you can use whatever is in your shed.
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