Backflow testing & repair in Cupertino, CA
Cupertino (Santa Clara County) gets its water from 2 suppliers, and the one on your water bill sets your backflow rules:
- San Jose Water: San Jose 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
- San Jose Water; California Water Service – Los Altos Suburban District
- Annual test
- San Jose 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
- 95014
San Jose Water rules for Cupertino customers
- Testing and recordkeeping are required on every backflow preventer at least once a year.
Source: San Jose Water backflow program (official page), checked October 17, 2026.
Rules for new and replacement devices in Cupertino
San Jose Water
- San Jose Water requires a reduced pressure (RP) assembly under most conditions; a double check assembly needs its prior approval.
- Systems with pumps require an air gap.
- Assemblies must be on the USC Foundation list of approved assemblies; check with the Backflow Department before buying one.
- All new assemblies have had to be lead-free since September 1, 2016.
Source: San Jose Water backflow program (official page).
Cal Water Los Altos
- 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 Cupertino property owners
Which water supplier serves Cupertino?
Cupertino is split between San Jose Water 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 San Jose Water customers in Cupertino?
San Jose Water tests backflow assemblies for its customers itself, at no charge.
Who tests backflow devices for Cal Water Los Altos customers in Cupertino?
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.