Saturated pH
Saturated pH (pHs) is the theoretical pH at which pool water would be exactly in equilibrium with calcium carbonate, used in LSI calculation.
Definition
Saturated pH (pHs) is the theoretical pH at which pool water would be exactly in equilibrium with calcium carbonate, used in LSI calculation.
Typical Values: pHs for typical pools: 7.5–8.0 depending on hardness, alkalinity, and temperature
In Plain Language
pHs is the pH at which water is exactly saturated with calcium carbonate given its current temperature, calcium hardness, and alkalinity. The LSI is calculated as: LSI = pH - pHs. If the actual pH is above pHs, the water is over-saturated (positive LSI). If below, under-saturated (negative LSI). The pHs is calculated from temperature, calcium hardness, and total alkalinity.
Why It Matters
pHs is the central concept in LSI calculation. Understanding it shows why raising pH to 7.8 in warm, hard water creates a severe scaling risk.
Typical Values
pHs for typical pools: 7.5–8.0 depending on hardness, alkalinity, and temperature
Last reviewed: 2026-06-01