Pool Acid Demand Calculator
Estimate the muriatic acid needed to lower your pool's pH to a target level.
Based on standard muriatic acid (31.45%, or 20° Baumé): about 12.8 fluid ounces per 10,000 gallons lowers pH by roughly 0.2. High total alkalinity makes pH stubborn, so you may need a bit more. Add acid in stages with the pump running, wait a few hours, and retest — it's easy to overshoot.
How it works
Pool pH creeps up over time, and high pH makes chlorine sluggish and the water prone to scale and cloudiness. Muriatic acid brings it back down into the sweet spot of about 7.4 to 7.6.
This uses a standard dosing rate for full-strength muriatic acid (31.45%, or 20° Baumé): roughly 12.8 fluid ounces per 10,000 gallons lowers pH by about 0.2. We scale that to your pool's volume and the size of the pH drop you want.
Dropping a 15,000-gallon pool from 8.0 to 7.5 is a 0.5 change, which comes out to roughly 48 fluid ounces. Because high alkalinity resists pH change, add acid in portions with the pump running, wait a few hours, and retest instead of dumping it all in at once.
Frequently asked questions
Muriatic acid or dry acid?
Both lower pH. Liquid muriatic acid is cheaper and works fast; dry acid (sodium bisulfate) is safer to store and handle but adds sulfates over time. This calculator is figured for liquid muriatic at full strength.
Why does alkalinity matter?
Total alkalinity buffers pH, so water with high alkalinity fights back against acid and needs more to move. If your pH keeps climbing right back up, your alkalinity is probably too high and worth lowering first.
How do I add acid safely?
Always add acid to water, never the reverse, with the pump running so it disperses. Pour slowly around the deep end, keep it off your skin and out of your eyes, and never mix it with chlorine products.