Calculate dosages to balance your pool's pH. Protect swimmers and equipment by maintaining the ideal 7.4-7.6 pH range for maximum chlorine effectiveness.
Enter your pool volume, your current pH reading, and your target pH. The ideal range is 7.4–7.6, which matches the pH of human tears and eyes and is the band where chlorine sanitizes efficiently without irritating swimmers, per long-standing PHTA/APSP water-balance guidance. Test pH at a stable time of day, ideally with the pump running and away from a fresh chemical addition, because aeration and recent dosing temporarily skew the reading. Crucially, check your Total Alkalinity before adjusting pH: alkalinity is the buffer that resists pH change, so if it is far out of range the pool will fight your corrections. The calculator also needs your acid or base of choice. To lower pH you will typically use muriatic acid (hydrochloric, often 31.45%) or dry acid (sodium bisulfate); to raise pH you will use soda ash (sodium carbonate) or, for gentler moves, aeration alone. Knowing alkalinity alongside pH lets you predict how stubbornly the water will hold its new value.
Acid and base demand both scale with volume and with how far and how buffered the water is, so doses are estimates you refine by retesting. A practical guide for muriatic acid (31.45%) to lower pH: roughly 0.6 quart (about 20 fl oz) per 10,000 gallons drops pH from about 7.8 to 7.5 when alkalinity sits near 100 ppm. Worked example: a 20,000-gallon pool reading 8.0 with normal alkalinity needs about 2 quarts (≈1.9 liters) of muriatic acid to reach 7.5 — add roughly three-quarters of that first, then retest. To raise pH, soda ash works at about 6 oz per 10,000 gallons to lift pH from 7.2 to 7.5, but it also nudges alkalinity up. In metric, lowering 75,000 liters by 0.3 pH units takes on the order of 1.1 liters of 31.45% muriatic acid. Higher alkalinity means more acid is required for the same pH drop.
pH is the master variable that decides whether your chlorine actually works: at pH 8.0 hypochlorous acid — the active sanitizing form — is only about a third as effective as at pH 7.2, so a 'clean' pool with high pH can still grow algae. It also governs corrosion and scale: low pH dissolves grout, etches plaster, and attacks metal heat exchangers, while high pH clouds water and deposits scale. Safety first when handling acid: always add acid to water, never water to acid, pour slowly at a return jet with the pump running, and wear eye protection. Dose in stages — add about 75% of the calculated amount, wait an hour with the pump circulating, then retest before adding more, because overshooting acid is far harder to reverse than coming up short. Never mix acid with chlorine. Recheck pH 6 hours later and again the next day, since aeration and dosing can let it climb back.
The ideal pool pH is 7.2-7.6, with 7.4 considered the sweet spot. That range is comfortable for swimmers' eyes and skin and keeps chlorine effective; below 7.0 the water turns corrosive, while above 7.8 chlorine weakens and scale forms.
To raise pH, add soda ash (sodium carbonate); for a small lift, aerating the water also nudges pH up by off-gassing CO2. Dissolve the soda ash in a bucket of water first, add it slowly with the pump running, and retest after a few hours since it can also raise Total Alkalinity.
Muriatic acid or dry acid (sodium bisulfate) are the most effective ways to lower pH. Always add acid to water, never water to acid, and pour slowly.
This is often caused by aeration (spas, waterfalls) which off-gasses CO2, or by the natural process of saltwater chlorine generators.
Yes. At a pH of 8.0, chlorine is only about 25% as active as it is at a pH of 7.2. Maintaining 7.4-7.6 is critical for keeping your pool clean.
It depends on the product. Liquid chlorine (sodium hypochlorite) and cal-hypo are alkaline and push pH upward, while trichlor and dichlor tablets are acidic and pull pH down. That is why your pH tends to drift in different directions depending on which chlorine you use, so factor your sanitizer in when you balance pH and alkalinity.