Backflow testing & repair in San Jose, CA
San Jose (Santa Clara County) gets its water from 3 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.
- San José Municipal Water System: you hire a certified tester. We test, file the results with San José Municipal Water, and repair failed devices.
- Great Oaks Water Company: you hire a certified tester. We test, file the results with Great Oaks Water, and repair failed devices.
- County
- Santa Clara County
- Water suppliers
- San Jose Water; San José Municipal Water System; Great Oaks Water Company
- Annual test
- San Jose Water: the supplier tests, San José Municipal Water: owner hires a certified tester and Great Oaks Water: owner hires a certified tester
- Our price
- $199 per device ($25 off for new customers), or from $180/year on a plan
- ZIP codes
- 95110, 95111, 95112, 95113, 95116, 95117, 95118, 95119, 95120, 95121, 95122, 95123, 95124, 95125, 95126, 95127, 95128, 95129, 95130, 95131, 95132, 95133, 95134, 95135, 95136, 95138, 95139, 95148
San Jose Water rules for San Jose 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.
San José Municipal Water rules for San Jose customers
- Testing and maintenance of backflow assemblies are the account holder’s or property owner’s responsibility.
- Muni Water recommends hose bib vacuum breakers on all outdoor and indoor hose connections.
Source: San José Municipal Water backflow program (official page), checked October 19, 2026.
Great Oaks Water rules for San Jose customers
- The program is administered for Great Oaks Water by BSI Online, where test status can also be checked.
- Questions about the program go to backflow@greatoakswater.com.
Source: Great Oaks Water backflow program (official page), checked October 19, 2026.
Rules for new and replacement devices in San Jose
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).
San José Municipal Water
- Where an onsite hazard assessment is needed, Muni Water decides the process case by case and tells the owner.
Source: San José Municipal Water 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 San Jose property owners
Which water supplier serves San Jose?
San Jose is split between San Jose Water, San José Municipal Water System and Great Oaks Water Company. Your water bill names your supplier, and its notice sets your backflow rules.
Who tests backflow devices for San Jose Water customers in San Jose?
San Jose Water tests backflow assemblies for its customers itself, at no charge.
Who tests backflow devices for San José Municipal Water customers in San Jose?
Muni Water does not test customers’ backflow assemblies: the account holder or property owner must hire a third-party backflow tester certified by the American Water Works Association.
Who tests backflow devices for Great Oaks Water customers in San Jose?
Great Oaks Water’s cross-connection program uses registered testing companies, which customers can look up through the program’s online system.