Low pH is corrosive to surfaces and equipment and hard on swimmers. Here's how to bring it up safely with soda ash — with the exact amount for your gallons.
Aim for roughly 7.4–7.6. Below about 7.2, water becomes aggressive: it can etch plaster, corrode metal fittings and heater components, and sting eyes and skin. The calculator above opens on the Raise pH mode — enter your gallons and current pH for the soda ash dose.
Soda ash (sodium carbonate) is the standard choice. Pre-dissolve it in a bucket of pool water and broadcast it slowly with the pump running, so it doesn't cloud the water or settle. Add conservatively and retest — soda ash raises pH quickly and also nudges total alkalinity up. If both pH and alkalinity are low, soda ash helps both; if only pH is low, add gently to avoid overshooting.
Common causes include heavy rain, low total alkalinity (which lets pH swing), acidic fill water, and overuse of pH-down or chlorine tablets (trichlor is acidic). If pH keeps dropping, check and correct your total alkalinity first — stable alkalinity is what keeps pH from drifting.
Soda ash (sodium carbonate) is the standard. Aeration also raises pH slowly without chemicals. Borates can help stabilize pH over time. The calculator above gives a soda ash dose for your pool.
Baking soda (sodium bicarbonate) mainly raises total alkalinity and only nudges pH slightly. To raise pH meaningfully, soda ash is the right product; use baking soda when alkalinity is the number you need to raise.
Low pH won't harm swimmers acutely at mild levels, but it's corrosive to plaster, metal, and equipment over time and can cause eye and skin irritation. It's worth correcting promptly.