Household water treatment in Los Altos, CA.

Los Altos is served by Cal Water's Los Altos Suburban District, which also covers parts of Los Altos Hills, Mountain View and Sunnyvale. It blends local groundwater with treated surface water bought from Valley Water and disinfects with chloramine.

What Cal Water reports for Los Altos

Cal Water's 2025 report for the Los Altos Suburban District puts groundwater hardness at an average of 305 ppm, which its own scale calls very hard, while the Valley Water supply averages 97 ppm. The district's water is chloraminated, with total chlorine averaging 1.5 ppm, which is the taste and smell some homeowners ask us about.

The way we work does not change from house to house. We look up the public data on your water, tell you what your home actually needs, and put it in for one all-in price.

What we fit in Los Altos homes

• A softener and carbon filter for the whole house, fitted on your main line, as the flagship bundle starting at $2,699 installed.
• Reverse osmosis under the sink for drinking water, and the part of the setup that deals with PFAS.

Done locally

In Los Altos we pair the softener with a carbon filter for the chloramine and fit both at the point your main line comes in.