Backflow testing & repair in Foster City, CA
BackflowCare tests backflow prevention assemblies in Foster City (San Mateo County) and files the results with Estero Municipal Improvement District. Estero Municipal Improvement District (Foster City’s water supplier) requires an annual test by a tester on San Mateo County’s authorized backflow tester list, as part of the County’s cross-connection program. If a device fails, we make minor repairs and file the passing retest with Estero MID.
- County
- San Mateo County
- Water supplier
- Estero Municipal Improvement District
- Annual test
- Estero MID: owner hires a certified tester
- Our price
- $199 per device ($25 off for new customers), or from $180/year on a plan
- ZIP codes
- 94404
What Estero MID requires in Foster City
- 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.
Backflow questions from Foster City property owners
Which water supplier serves Foster City?
Estero Municipal Improvement District supplies water in Foster City (ZIP 94404) and runs its backflow program.
Who tests backflow devices for Estero MID customers in Foster City?
Estero Municipal Improvement District (Foster City’s water supplier) requires an annual test by a tester on San Mateo County’s authorized backflow tester list, as part of the County’s cross-connection program.
When is the backflow test due in Foster City?
The tester sends the test report to County Environmental Health within 10 calendar days.
Does Estero MID charge its own fee in Foster 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.