Pool pH Calculator
Enter your pH reading and target. The calculator picks soda ash to raise it, or acid to lower it. This is a starting estimate, so add part, wait and retest.
Quick answer: For a 10,000-gallon pool, lowering pH by 0.2 takes about 12 fl oz of muriatic acid or 16 oz of dry acid. Raising it 0.2 takes about 6 oz of soda ash.
Checked against 4 published sources (see them). Updated October 2026.
- Lowers pH by about
- 0.3
- Next step
- Add in stages
- Add about half, run the pump for an hour, retest, then add more if needed.
How it works
This uses the rule of thumb published by two county health departments (Lucas County, Ohio and Yakima County, Washington): per 10,000 gallons, each 0.2 change in pH takes about 6 oz of soda ash to raise it, or about 12 fl oz of muriatic acid or 1 lb of dry acid to lower it.
Real doses depend on your total alkalinity (TA). Higher alkalinity resists pH change, so it takes more chemical. That's why this is a starting estimate: add part, let it circulate, and retest.
Soda ash also raises alkalinity a little. Acid lowers alkalinity a little.
Tips
- Always add acid to water, never water to acid. Pour slowly in front of a return jet with the pump running.
- Never add acid and chlorine at the same time or in the same spot.
- If pH keeps drifting up, test total alkalinity. High alkalinity is a common cause.
Sources
We checked the math on this page against:
- Lucas County (Ohio) Health Department: Pool Chemistry Adjustments
- Yakima County (Washington): Chemical Dosing
- Wojtowicz, "Swimming Pool and Spa Water Chemical Adjustments," Journal of the Swimming Pool and Spa Industry (2004)
- CDC: Home pool and hot tub water treatment and testing
Frequently asked questions
How much muriatic acid lowers pH in a 15,000-gallon pool?
As a starting point, about 18 fl oz to drop pH by 0.2. Add half, wait an hour with the pump running, and retest.
What should pool pH be?
The CDC recommends keeping pH between 7.0 and 7.8. Many pool owners aim for 7.4–7.6.
Why is my pH still off after adding the amount?
Alkalinity changes how much pH moves. These amounts are a starting estimate. Retest and adjust in small steps.