Soda ash raises pH and alkalinity. Usually, if you try to use it to raise pH, you will raise the alkalinity too high and have to add acid to adjust it back down.

Does soda ash raise total alkalinity?

Baking Soda and pH Levels Note that soda ash does also raise alkalinity along with pH. That six ounces of soda ash will raise your alkalinity by about 5 ppm, so only use soda ash if you want to raise alkalinity and pH.

Does soda ash raise pH and alkalinity?

The industry standard has always been to use sodium bicarbonate (baking soda) to raise total alkalinity and sodium carbonate (soda ash) to raise pH — the exception being if both total alkalinity and pH are low. … Sodium carbonate will actually have a dramatic effect on both pH and total alkalinity.