How to Lower pH in a Pool (and Raise It When It's Too Low)
The ideal pool pH is 7.2 to 7.8. Here's how to bring it down with muriatic or dry acid, how to raise it with soda ash or aeration, and why it keeps drifting.
pH measures how acidic or basic the water is. Pool water should sit between 7.2 and 7.8. Too high, and chlorine works poorly, water clouds and scale forms. Too low, and it stings eyes and eats metal, plaster and vinyl.
How to lower pH
You need an acid. Two kinds are sold for pools:
| Product | Form | Notes |
|---|---|---|
| Muriatic acid (hydrochloric, about 31%) | Liquid | Cheapest per dose. Fumes: handle outdoors, with goggles and gloves |
| Dry acid (sodium bisulfate) | Granules | Easier to handle. Adds sulfates over time |
Steps:
- Test pH and total alkalinity.
- With the pump running, pour the acid slowly into the deep end in front of a return jet, or dilute it first in a bucket of pool water. Always add acid to water, never water to acid.
- Start small. About 8 fl oz (one cup) of muriatic acid per 10,000 gallons is a cautious first dose. Then wait an hour and retest.
- Repeat until pH is where you want it.
The exact amount depends on your alkalinity, which is why small steps beat any single formula. It is also why our pool chemical calculator doesn’t guess acid doses.
How to raise pH
The short version is below. Our full guide covers doses and causes: how to raise pH in a pool.
- Aeration raises pH without raising alkalinity much. Point return jets up so they break the surface, run a waterfall or fountain, or use a hose with a spray nozzle across the surface. It is slow, but you can’t overshoot.
- Soda ash (sodium carbonate) raises pH fast and alkalinity a little. Dissolve it in a bucket first and add it in front of a return.
- Borax raises pH with a smaller effect on alkalinity.
If alkalinity is also low (under about 60 ppm), raise it first with baking soda. The pool chemical calculator gives the amount. Low alkalinity lets pH swing with every rain and dose.
Why pH keeps drifting
It keeps rising: carbon dioxide escapes from the water, and the higher the alkalinity, the more it escapes. Waterfalls, spas, heavy splashing and salt chlorine generators all speed this up. Keeping alkalinity at the low end (60–80 ppm) slows the drift.
It keeps falling: trichlor tablets are very acidic and pull pH down every day. So do heavy rain and acid overdoses. If you use tablets, check pH twice a week. Our comparison of liquid chlorine vs tablets explains why.
Safety
- Never mix acid with chlorine. They release chlorine gas.
- Store acid and chlorine apart, ideally in different rooms.
- Wear goggles and gloves, and rinse spills with lots of water.
Run the numbers for your pool
Using your saved pool: . My pool
4 chemicals to add
Add them one at a time, a few hours apart, with the pump running. Never mix chemicals together.
- Pool size
- 15,000 gal
- Chlorine target
- 4 ppm
- Stabilizer target
- 40 ppm
What to add
- 6.3 lbBaking soda (sodium bicarbonate) to raise alkalinity by 30 ppm
- 18 lbCalcium chloride (dihydrate, 77–80%) to raise hardness by 100 ppm
- 2.5 lbStabilizer (cyanuric acid) to raise CYA by 20 ppm. Dissolves slowly: use a sock in the skimmer
- 57.6 fl ozLiquid chlorine 10% to raise free chlorine by 3 ppm
What would change your result
Read every product label and follow its safety directions.
Quick answers
What is the ideal pH for a pool?
Between 7.2 and 7.8. Many owners aim for 7.4 to 7.6: comfortable for eyes, gentle on equipment, and chlorine still works well.
Can I swim after adding muriatic acid?
Wait until it has mixed with the pump running, usually about 30 minutes to an hour, then retest. Follow the label's re-entry time if it gives one.
Will baking soda raise pH?
Only a little. Baking soda mainly raises total alkalinity. To raise pH itself, use soda ash (sodium carbonate) or aerate the water.
Why does my pool pH keep going up?
Water loses carbon dioxide to the air, which pushes pH up, especially with high alkalinity, waterfalls, spillovers or a salt chlorine generator. Lowering alkalinity toward 60–80 ppm slows the rise.
Pool costs in your state
What a pool pump and a hot tub cost to run at your state's electricity price.
Keep reading
- How to Raise pH in a Pool: Soda Ash, Aeration or BoraxLow pool pH stings eyes and eats equipment. Here's how to raise it with aeration, soda ash or borax, how much to start with, and why it keeps dropping.
Pool Green but Chlorine Is High? 4 Real Causes and FixesA green pool with a high chlorine reading usually means metals, too much stabilizer, a misleading test or pollen. Here's how to tell which one you have and what to do.
Pool Salt Cell Guide: How It Works, Cleaning and Low Salt ReadingsHow a pool salt cell makes chlorine, how to clean it, how long it lasts, and why it reads 'low salt' when the water isn't. A practical guide for salt pool owners.