Soda Ash Pool Calculator
Low pH makes water sting and eats at metal and plaster. Enter your pool size and readings to see how much soda ash brings it back up.
Updated November 2026
How Much Soda Ash Raises Pool pH?
About 6 ounces of soda ash per 10,000 gallons raises pH by roughly 0.2. A 15,000 gallon pool going from 7.0 to 7.4 needs about 18 ounces, a little over a pound.
The exact change depends on your total alkalinity, so add the dose, circulate for 2 to 3 hours and retest before adding more.
Soda Ash Dosing Chart
Soda ash needed by pool size and how far you are raising pH:
| Raise pH by | 10k gal | 15k gal | 20k gal | 25k gal | 30k gal |
|---|---|---|---|---|---|
| +0.2 | 6 oz | 9 oz | 12 oz | 15 oz | 1.1 lbs |
| +0.4 | 12 oz | 1.1 lbs | 1.5 lbs | 1.9 lbs | 2.2 lbs |
| +0.6 | 1.1 lbs | 1.7 lbs | 2.2 lbs | 2.8 lbs | 3.4 lbs |
| +0.8 | 1.5 lbs | 2.2 lbs | 3 lbs | 3.8 lbs | 4.5 lbs |
Based on 6 oz per 10,000 gallons for each 0.2 of pH. Pools with high alkalinity need more and pools with low alkalinity need less. Split anything over 0.4 into two doses.
When should I use soda ash?
Use soda ash (sodium carbonate, sold as pH increaser or pH up) when pH is below 7.2. It raises pH strongly and raises total alkalinity a little: each 6 oz per 10,000 gallons adds about 4 to 5 ppm of alkalinity.
- pH low, alkalinity low or normal: soda ash is the right choice.
- pH fine, alkalinity low: use baking soda instead. The baking soda calculator gives the amount.
- pH low, alkalinity already high: borax or aeration raises pH with less effect on alkalinity. See baking soda vs soda ash vs borax.
How do I add soda ash without clouding the pool?
- Test pH and total alkalinity, and confirm your pool volume with the volume calculator.
- Dissolve the dose in a bucket of pool water. Add the powder to the water, not the other way around.
- Pour it slowly around the edge of the pool with the pump running.
- Add no more than about 1 lb per 10,000 gallons at one time.
- Retest after 2 to 3 hours of circulation and repeat only if pH is still low.
Why does pool pH keep dropping?
- Chlorine tablets. Trichlor tablets are acidic and pull pH and alkalinity down week after week.
- Rain. Rainwater is slightly acidic and dilutes alkalinity.
- Low alkalinity. Below about 80 ppm there is too little buffer to hold pH steady.
- Heavy use and fresh fill water can both move pH, depending on your water supply.
Frequently Asked Questions
How much soda ash does it take to raise pH 0.2?
About 6 ounces per 10,000 gallons. A 20,000 gallon pool needs about 12 ounces for the same change.
Is soda ash the same as baking soda?
No. Soda ash is sodium carbonate and raises pH strongly. Baking soda is sodium bicarbonate and mainly raises total alkalinity.
How long after adding soda ash can I swim?
Wait about an hour with the pump running, until the water is clear and pH tests at 7.8 or below.
Can I add too much soda ash?
Yes. Too much pushes pH above 7.8, which weakens chlorine, clouds the water and leads to scale. If you overshoot, a small dose of acid brings it back. The muriatic acid calculator gives the amount.
Can I use washing soda from the laundry aisle?
Yes, if the box lists only sodium carbonate, with no scent or detergent. It is the same chemical as pool pH increaser.
Sources
- Hayward: AquaRite owner's manual, water chemistry and saturation index
- CDC: Pool chemical injuries and how to prevent them (MMWR, 2019)
Next: balance the rest
Once pH is in range, check alkalinity, chlorine and stabilizer.
Related: Baking soda calculator · Muriatic acid calculator · What order to add chemicals