Agency-approved testers serving Ontario
Every tester below is on a local water-agency approved list. Claimed & verified businesses appear first; the rest can be reached at their agency-published number.
OB
Ontario Backflow Co.on City of San Bernardino Municipal Water's approved list · Aug 2026
Ontario, CA(310)386-6063
SM
SM Waterworks Backflow Serviceon City of San Bernardino Municipal Water's approved list · Aug 2026
Ontario, CA(909)828-1512
Backflow testing requirements in Ontario
Property owners in Ontario served by City of Ontario Utilities are required to have their backflow prevention assemblies tested annually. If you've received a testing notice, a certified tester can complete the test and file your results directly with your water agency — keeping your property compliant with no paperwork on your end.
Ontario zip codes served: 91758, 91761, 91762, 91764