Pool pH calculator
Lower pH with the exact amount of acid for your jug's strength, or raise it the way Trouble Free Pool does: aeration first, then borax. The dose accounts for your alkalinity and where your pH starts.
- Raise free chlorine 10 ppm
- ~107 fl oz liquid (12.5%) (3.3 qt; 3.2 L), ~19 oz cal-hypo (70%) (539 g), or ~22 oz dichlor (62%) (624 g)
- Raise alkalinity (TA) 10 ppm
- ~1.5 lb baking soda (680 g)
- Raise calcium (CH) 10 ppm
- ~1.2 lb calcium chloride (77% flake) (544 g)
- Raise stabilizer (CYA) 10 ppm
- ~13 oz cyanuric acid (369 g)
- Lower pH 8.0 → 7.6 (at TA 100)
- ~10 fl oz muriatic acid (1.3 cups; 296 mL), or ~0.9 lb dry acid (408 g)
Ballpark for a 10,000-gallon pool. Enter your size and levels below for your exact dose.
Example numbers are filled in so you can see an answer. Type your own over them.
Don't know your gallons? Work it out here →
Exact geometry at 7.48 gal/ft³. Kidney shapes, diving hoppers and salt/turnover figures live in the full Pool Volume Calculator.
Muriatic acid to lower pH
| TA (ppm) | 7.8 → 7.6, 10,000 gal (37,854 L) | 8.0 → 7.6, 10,000 gal (37,854 L) | 8.0 → 7.6, 20,000 gal (75,708 L) |
|---|---|---|---|
| 60 | 3.8 fl oz (112 mL) | 6.7 fl oz (198 mL) | 13.3 fl oz (1.7 cups; 393 mL) |
| 80 | 4.9 fl oz (145 mL) | 8.5 fl oz (1.1 cups; 251 mL) | 16.9 fl oz (2.1 cups; 500 mL) |
| 100 | 5.9 fl oz (174 mL) | 10.3 fl oz (1.3 cups; 305 mL) | 20.5 fl oz (2.6 cups; 606 mL) |
| 120 | 7.0 fl oz (207 mL) | 12.1 fl oz (1.5 cups; 358 mL) | 24.1 fl oz (3 cups; 713 mL) |
Borax or soda ash to raise pH
| TA (ppm) | Borax, 7.2 → 7.6 | Soda ash, 7.2 → 7.6 |
|---|---|---|
| 60 | 1.8 lb (816 g) | 14.2 oz (403 g) |
| 80 | 2.2 lb (998 g) | 1.1 lb (499 g) |
| 100 | 2.7 lb (1.2 kg) | 1.4 lb (635 g) |
| 120 | 3.2 lb (1.5 kg) | 1.6 lb (726 g) |
Why the dose depends on where pH starts
Alkalinity resists pH change most strongly near 7.2 to 7.4 and less as pH climbs. So bringing pH down from 8.0 takes much less acid per tenth than bringing it down from 7.6. Many calculators use one flat number per 0.1 of pH, which over-doses the most common correction (a pool drifting to 8.0). Ours uses the pH model from Trouble Free Pool's PoolMath, which accounts for it.
Safety
- Pour acid slowly into the deep end in front of a return, pump running. Never splash it on the plaster.
- Never drop pH more than about 0.4 at once. Retest before adding more.
- Add acid to water, never water to acid. Keep it away from chlorine, always.
- On a salt pool, use muriatic, not dry acid: dry acid adds sulfates, and some cell makers advise against it.
More: pool pH explained.
pH doses: Trouble Free Pool PoolMath's pH model (buffer factor by mid-pH, TA and borates). Half-strength acid scaled by weight percent and density. Targets: Trouble Free Pool's ideal levels.
FAQ
How much muriatic acid do I add to lower pH?
It depends on your gallons, your alkalinity and where your pH starts, because the same 0.4 drop takes less acid from 8.0 than from 7.6. In 10,000 gallons at TA 80, taking pH from 8.0 to 7.6 takes about 8.5 fl oz (1.1 cups; 251 mL) of 31.45% muriatic acid. Add about three-quarters, run the pump, and retest.
What should my pool pH be?
Aim for 7.6 to 7.8. Anywhere from 7.2 to 8.0 is acceptable. The 7.4–7.6 figure you will see elsewhere is written for public pools without stabilizer; with CYA in the water, pH matters less to chlorine strength.
How do I raise pH in my pool?
Trouble Free Pool's order: aerate first (it is free and adds nothing). If you still need a chemical and alkalinity is 50 or higher, use borax. If alkalinity is under 50, raise it with baking soda first. Soda ash raises pH too but pushes alkalinity up a lot, which drives pH back up later.
Is half-strength acid the same as muriatic acid?
It is the same chemical with more water. Because acid strength is a percent by weight and the weaker acid is less dense, you pour a little more than twice as much: about 19.8 fl oz (2.5 cups; 586 mL) of 14.5% for the same change that takes 8.5 fl oz (1.1 cups; 251 mL) of 31.45%. Check the percentage on your own jug and pick it in the calculator.
Why does my pool pH keep going up?
Mostly carbon dioxide leaving the water, which happens faster at higher alkalinity and with more splashing. Lowering total alkalinity toward 60–80 slows the rise. Salt pools rise faster, and the exact reason at the cell is still debated.