Backflow testing & repair in Sunnyvale, CA
Sunnyvale (Santa Clara County) gets its water from 2 suppliers, and the one on your water bill sets your backflow rules:
- City of Sunnyvale Water: you hire a certified tester. We test, file the results with City of Sunnyvale, and repair failed devices.
- 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
- City of Sunnyvale Water; California Water Service – Los Altos Suburban District
- Annual test
- City of Sunnyvale: owner hires a certified tester 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
- 94085, 94086, 94087, 94089
City of Sunnyvale rules for Sunnyvale customers
- If the City’s inspection finds you need a backflow device, it notifies you within 30 days with a letter included in your utility bill.
- The City offers free inspections to help residents and businesses check whether they comply.
- Lawn irrigation and fire sprinkler systems need an approved backflow prevention device.
- Private wells must also have proper backflow protection.
- Water service may be disconnected if requirements aren’t met after repeated requests.
Source: City of Sunnyvale backflow program (official page), checked October 19, 2026.
Rules for new and replacement devices in Sunnyvale
- 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 Sunnyvale property owners
Which water supplier serves Sunnyvale?
Sunnyvale is split between City of Sunnyvale 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 City of Sunnyvale customers in Sunnyvale?
Sunnyvale requires backflow devices to be maintained and tested every year, and publishes a list of approved backflow testing contractors.
Who tests backflow devices for Cal Water Los Altos customers in Sunnyvale?
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.
When is the backflow test due in Sunnyvale for City of Sunnyvale customers?
If the City’s inspection finds you need a backflow device, it notifies you within 30 days with a letter included in your utility bill.