Backflow testing & repair in Daly City, CA
Daly City (San Mateo County) gets its water from 2 suppliers, and the one on your water bill sets your backflow rules:
- Daly City Department of Water & Wastewater Resources: you hire a certified tester. We test, file the results with Daly City Water, and repair failed devices.
- California Water Service – Bayshore District: you hire a certified tester. We test, file the results with Cal Water Bayshore, and repair failed devices.
- County
- San Mateo County
- Water suppliers
- Daly City Department of Water & Wastewater Resources; California Water Service – Bayshore District
- Annual test
- Daly City Water: owner hires a certified tester and Cal Water Bayshore: owner hires a certified tester
- Our price
- $199 per device ($25 off for new customers), or from $180/year on a plan
- ZIP codes
- 94014, 94015
Daly City Water rules for Daly City customers
- In the San Mateo County program, only a County-certified backflow tester may test assemblies.
- Assemblies must be tested at least once a year, and again after installation or repair.
- The tester sends the test report to County Environmental Health within 10 calendar days.
- Late testing can bring administrative fines of up to $500 per day, per assembly.
Source: San Mateo County Environmental Health cross-connection program (official page), checked October 19, 2026.
Rules for new and replacement devices in Daly City
- 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 Bayshore 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 Daly City property owners
Which water supplier serves Daly City?
Daly City is split between Daly City Department of Water & Wastewater Resources and California Water Service – Bayshore District. Your water bill names your supplier, and its notice sets your backflow rules.
Who tests backflow devices for Daly City Water customers in Daly City?
Daly City’s backflow testing falls under San Mateo County Environmental Health’s cross-connection control program.
Who tests backflow devices for Cal Water Bayshore customers in Daly City?
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 Daly City for Daly City Water customers?
The tester sends the test report to County Environmental Health within 10 calendar days.
Does Daly City Water charge its own fee in Daly City?
Yes. Late testing can bring administrative fines of up to $500 per day, per assembly. That fee is separate from our $199 test price.