PooloraHow much soda ash to add to a pool
Soda ash raises pH quickly, and alkalinity with it. Here is how much for your pool size, and how to keep from overshooting.
- 15,000 gallons, pH 7.2 → 7.5 (alkalinity 80): 1.5 lb (25 oz · 700 g) of soda ash.
- If alkalinity is low, raise it with baking soda first.
- Add half, circulate, retest.
Chart: soda ash by pool size
With total alkalinity at 80 ppm (water at 80 °F, calcium 300, stabilizer 40):
| Pool size | pH 7.0 → 7.4 | pH 7.2 → 7.5 |
|---|---|---|
| 5,000 gal | 14.5 oz 410 g | 8 oz 235 g |
| 10,000 gal | 1.8 lb 820 g | 1 lb 465 g |
| 15,000 gal | 2.7 lb 1.25 kg | 1.5 lb 700 g |
| 20,000 gal | 3.6 lb 1.65 kg | 2.1 lb 935 g |
| 25,000 gal | 4.5 lb 2.05 kg | 2.6 lb 1.15 kg |
| 30,000 gal | 5.4 lb 2.45 kg | 3.1 lb 1.4 kg |
With higher alkalinity you need more soda ash for the same change; how to raise pH has the comparison.
Work out your dose
Example: a 20,000-gallon pool at pH 7.2 with alkalinity 80 needs about 2.1 lb (33 oz · 935 g) of soda ash to reach 7.5. If your alkalinity is different, Poolora recalculates it with your reading.
Overshot it?
If pH ends above 7.8, bring it back with acid; see how much muriatic acid. That is why adding half first pays off.
Avoid cloudy water
- Pre-dissolve soda ash in a bucket of pool water and pour it slowly in front of a return, pump running.
- A big dose all at once can turn the water hazy for a while, especially with high calcium.
- Add about half, let it circulate and retest before adding the rest.
Soda ash or baking soda?
Soda ash (sodium carbonate) is for pH; baking soda (sodium bicarbonate) is for alkalinity. If both are low, start with baking soda: fixing alkalinity often brings pH up enough on its own. If alkalinity is already where you want it, aeration raises pH without adding any.
Common questions
Is "pH up" the same as soda ash?
Most "pH up" or "pH increaser" products are soda ash. Check the label for sodium carbonate.
Why did the pool turn cloudy after soda ash?
Raising pH quickly can make calcium come out of solution for a while. Keep filtering; it usually clears. Next time pre-dissolve and add less at once.
Do it with your own products
Poolora turns your test into the exact amount of the products on your shelf, in cups and ounces, in the right order, and tells you when it's safe to swim. Free to start; every chemical, water balance and history are part of Pro.
Keep going
Sources
- ANSI/APSP/ICC-11 (pH 7.2–7.8)
- Pool & Hot Tub Alliance (PHTA): alkalinity fact sheet
- Doses: Poolora engine (mass balance by product and strength; pH by a carbonate-equilibrium model with constants from the USGS PHREEQC database)