Household water treatment in Cupertino, CA.

Cupertino's city-owned water system is operated by San Jose Water, and part of Cupertino is served by Cal Water's Los Altos Suburban District instead. Both blend local groundwater with treated Valley Water.

Cupertino's water depends on who runs your pipe

San Jose Water reports the City of Cupertino system in its 2025 report, where Valley Water surface water averages 99 ppm hardness and its mountain supply 151 ppm. Homes on the Cal Water side draw on groundwater that Cal Water's 2025 report puts at an average of 305 ppm. Two Cupertino houses a few streets apart can start from noticeably different water.

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 Cupertino 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 Cupertino we check whether your bill comes from San Jose Water or Cal Water first, then size and fit the system at the point your water line comes into the house.