Operator terms · Water and wastewater
What is pH in water?
pH measures how acidic or basic water is, on a scale from 0 to 14, where 7 is neutral. It affects coagulation, disinfection, and corrosion, so operators watch and adjust it. Below 7 is acidic and can corrode pipes; above 7 is basic. Small pH changes matter more than they look.
Last reviewed 2026-08-03
Why operators watch it
Coagulation and disinfection each work best in a certain pH range, and low pH corrodes pipes. Keeping pH in range keeps treatment effective and the system safe.
The scale
The pH scale runs 0 to 14. Each whole step is a tenfold change, so a small number change is a large real change in acidity.
Common questions
- What is neutral pH?
- 7. Below 7 is acidic, above 7 is basic.
- Why does pH matter in treatment?
- It affects coagulation, disinfection, and corrosion.
- Can low pH damage pipes?
- Yes, acidic water is corrosive.