Although pH usually has no direct impact on water consumers, it is one of the most important
operational water-quality parameters. Careful attention to pH control is necessary at all stages
of water treatment to ensure satisfactory water clarification and disinfection. For effective
disinfection with chlorine, the pH should preferably be less than 8. The pH of the water
entering the distribution system must be controlled to minimize the corrosion of water mains2
and pipes in household water systems. Failure to do so can result in the contamination of
drinking-water and in adverse effects on its taste, odour, and appearance.
The optimum pH will vary in different supplies according to the composition of the water and
the nature of the construction materials used in the distribution system, but is often in the
range 6.5–9.5. Extreme pH values can result from accidental spills, treatment breakdowns,
and insufficiently cured cement mortar pipe linings.
No health-based guideline value is proposed for pH.