Hardness as CaCO3

Definition

The practice of reporting hardness ions such as calcium and magnesium as mg/L as CaCO3 so they share an equivalent basis with alkalinity.

Placing hardness and alkalinity on the same equivalent basis lets them be compared directly in softening calculations, scaling indices, and charge-balance relationships. Without that common basis, every comparison would require a separate molecular-weight conversion. Hardness is the calcium and magnesium pool that drives calcium carbonate scaling when carbonate is present.

Related concepts

mg or L as Calcium Carbonate · Boiler Makeup Softening · Charge Balance

---

Part of The Blueprint of Water · 📏 measurement