Backflow testing & repair in Los Altos Hills, CA
Los Altos Hills (Santa Clara County) gets its water from 2 suppliers, and the one on your water bill sets your backflow rules:
- Purissima Hills Water District: Purissima Hills Water tests devices itself; we make minor repairs.
- California Water Service – Los Altos Suburban District: you hire a certified tester. We test, file the results with Cal Water Los Altos, and repair failed devices.
- County
- Santa Clara County
- Water suppliers
- Purissima Hills Water District; California Water Service – Los Altos Suburban District
- Annual test
- Purissima Hills Water: the supplier tests and Cal Water Los Altos: owner hires a certified tester
- Our price
- $199 per device ($25 off for new customers), or from $180/year on a plan
- ZIP codes
- 94022, 94024
Purissima Hills Water rules for Los Altos Hills customers
- The annual testing fee started showing on water bills in September 2025.
Source: Purissima Hills Water backflow program (official page), checked October 19, 2026.
Rules for new and replacement devices in Los Altos Hills
- Only approved, testable backflow prevention assemblies may be installed at the water meter.
- Air gaps must also be inspected every year.
- The assembly installed must be the type Cal Water’s local cross-connection specialist specifies.
Source: Cal Water Los Altos backflow program (official page).
Installing or replacing a device takes a licensed plumbing contractor, usually with a permit. We can refer you to one we trust, test the new device once it’s in, and make minor repairs to existing ones.
Backflow questions from Los Altos Hills property owners
Which water supplier serves Los Altos Hills?
Los Altos Hills is split between Purissima Hills Water District and California Water Service – Los Altos Suburban District. Your water bill names your supplier, and its notice sets your backflow rules.
Who tests backflow devices for Purissima Hills Water customers in Los Altos Hills?
Since 2025, Purissima Hills Water District adds an annual backflow testing fee to the water bill of every customer with a backflow prevention device, so customers don’t arrange the annual test themselves.
Who tests backflow devices for Cal Water Los Altos customers in Los Altos Hills?
Property owners are responsible for their backflow assemblies, which Cal Water requires to be inspected and tested every year by a certified backflow prevention assembly tester.