# Backflow Testing St. Louis > Backflow testing in St. Louis: annual backflow preventer testing, repair and certification reports filed with your water provider. Typically $250–$500 per Canonical: https://legacyplumbingmo.com/commercial/backflow-prevention Last updated: 2026-10-28 Backflow Prevention & Testing RPZ, DCVA, and PVB install, repair, and annual certification for St. Louis commercial buildings — with the paperwork filed to your local water authority so you stay in compliance. [Schedule Backflow Service](https://legacyplumbingmo.com/contact-us) [Call 636-978-0120](tel:+16369780120) ## Schedule a Test or Install Tell us about your project — we respond within one business day. Backflow & Compliance ## Stay certified and inspection-ready. We provide annual backflow testing, repair, and replacement by certified testers, and we file your results with the water authority. We also handle grease interceptor maintenance to keep you compliant with MSD FOG requirements. [Schedule Testing](https://legacyplumbingmo.com/request-service) ### Includes - Annual backflow testing - Backflow repair and replacement - Results filed with the water authority - Grease interceptor maintenance (MSD FOG) ## Backflow Testing and Certification in St. Louis Backflow testing confirms that the backflow preventer on a building's water service, fire line or irrigation connection still keeps used water from flowing back into the public supply. Commercial assemblies, including reduced-pressure zone (RPZ), double-check valve (DCVA) and pressure-vacuum breaker (PVB) assemblies, are typically tested every year on the schedule your water provider sets. Certified testers use calibrated gauges, and the certified test report is filed with the local water authority on your behalf. Backflow preventer testing is required across restaurants and quick-service kitchens, healthcare and dental offices, multifamily buildings, schools and universities, industrial and warehouse facilities, retail, hotels and car washes. Property managers can put a whole portfolio on one annual program with one schedule, one invoice and every report filed. Legacy Plumbing serves St. Louis City, St. Louis County, St. Charles County and Jefferson County from our O'Fallon, MO shop, and has since 1996, with UA Local 562 crews. Testing is typically $250–$500 per assembly per year (estimate; final price depends on device size, number of devices and access), scheduled Monday–Friday, 7am–4pm. Related: [Backflow Compliance Checker](https://legacyplumbingmo.com/tools/backflow-compliance) · [Preventive Maintenance Plans](https://legacyplumbingmo.com/facility-services/preventive-maintenance) · [Commercial Water Heaters](https://legacyplumbingmo.com/facility-services/commercial-water-heaters) · [commercial plumbing contractors in St. Louis](https://legacyplumbingmo.com/commercial) Service areas: [St. Louis](https://legacyplumbingmo.com/locations/st-louis) · [St. Charles County](https://legacyplumbingmo.com/locations/st-charles-county) · [Jefferson County](https://legacyplumbingmo.com/locations/jefferson-county) Scope of Work ## Backflow Services for St. Louis Commercial Buildings From new install to annual certification — one certified team, one paperwork trail. ### RPZ Install & Replacement Reduced-pressure zone assemblies sized, installed, and certified for high-hazard commercial connections. View RPZ Install & Replacement details ### DCVA & PVB Install Double-check valve and pressure-vacuum breaker assemblies for fire mains and irrigation. View DCVA & PVB Install details ### Repair & Rebuild Rubber-goods kits, check repairs, and full rebuilds — same-day service so you stay in compliance. View Repair & Rebuild details ### Annual Certification Testing Certified testers, calibrated gauges, and reports filed with the local water authority on your behalf. View Annual Certification Testing details ### Failed Test Response If an assembly fails, we repair and retest fast — no shut-off notice from the water utility. View Failed Test Response details ### Cross-Connection Surveys Walkthroughs and risk assessments to identify unprotected cross-connections before the utility does. View Cross-Connection Surveys details What We Test ## RPZ, DCVA and PVB Assemblies We test reduced-pressure zone (RPZ), double-check valve (DCVA) and pressure-vacuum breaker (PVB) assemblies on the three lines where commercial buildings carry them: - Domestic water services - Fire sprinkler lines, coordinated with your fire sprinkler contractor - Irrigation systems [Check when your assemblies are due with our backflow compliance checker](https://legacyplumbingmo.com/tools/backflow-compliance) Failed Tests ## When an Assembly Fails - 1 ### Diagnose The tester identifies which check or relief valve failed and why. - 2 ### Repair or Rebuild Common rebuild parts ride on the truck, so most repairs happen on the same visit. - 3 ### Replace if Needed Assemblies that can't be rebuilt are replaced with a properly sized unit. - 4 ### Retest & Report We retest the assembly and handle the test report with your water provider. Why Legacy ## Certified Backflow Testers Across the St. Louis Metro Missouri-licensed backflow testers with calibrated gauges, parts on the truck, and direct working relationships with St. Louis–area water authorities. No back-and-forth, no missed annuals. - Missouri-licensed testers - Calibrated gauges on file - RPZ/DCVA parts in stock - Reports filed for you - Portfolio program management - Same-day repair & retest Who We Serve ## St. Louis Facilities We Keep Compliant Restaurants & QSR Healthcare & Dental Multi-Unit Residential Industrial & Warehouse Retail & Mixed-Use Schools & Universities Hotels & Hospitality Car Washes & Auto Annual Program ## How It Works Once you're on the program, we track the annual due date, schedule the test, file the paperwork, and only call you if something fails. - 1 ### Onboarding & Inventory We map every assembly across your portfolio with size, location, and current due dates. - 2 ### Scheduled Annual Test Certified test in line with your local St. Louis water authority's renewal date. - 3 ### Repair if Needed If anything fails, we repair on the same visit when possible and retest on the spot. - 4 ### Filed Documentation Certified test report submitted to the water authority and copied to your facilities team. FAQ ## St. Louis Commercial Backflow — FAQs - **What is backflow testing?:** Backflow testing checks that a backflow preventer, such as an RPZ, double-check valve or pressure-vacuum breaker, still stops used water from flowing back into the public supply. A certified tester uses calibrated gauges, records the results and files the test report with the local water authority. - **How often does a commercial backflow preventer need to be tested?:** Most commercial assemblies are tested annually, and your water provider sets the schedule and due date. Fire-line backflows also need annual testing, which we coordinate with your fire sprinkler contractor. Our free backflow compliance checker helps you see what applies to your building. - **Who files the backflow certification with the water utility?:** We do. After each annual test, Legacy Plumbing files the certified test report directly with your local water authority and copies your facilities team, so you don't receive a delinquency notice. Property managers can keep every building on one schedule with one paperwork trail. - **What happens if a backflow preventer fails its test?:** We repair or rebuild the assembly with rubber-goods kits, check repairs or a full rebuild, then retest, usually on the same visit when parts are on the truck. Once it passes, the certified report is filed so the building stays in compliance with the water utility. - **How much does commercial backflow testing cost?:** Annual backflow testing is typically $250–$500 per assembly per year (estimate; final price depends on device size, number of devices and access). Repairs, rebuilds or replacement assemblies are quoted separately if an assembly fails its test. Call 636-978-0120 Monday–Friday, 7am–4pm to schedule certified testing anywhere in St. Louis, St. Charles County or Jefferson County. ## Get an Annual Backflow Test Reminder We'll email you about a month before your next test is due. No spam — just the reminder. ### Related Services - [Backflow Compliance Checker](https://legacyplumbingmo.com/tools/backflow-compliance) - [Preventive Maintenance Plans](https://legacyplumbingmo.com/facility-services/preventive-maintenance) - [Plumbing in St. Charles County](https://legacyplumbingmo.com/locations/st-charles-county) - [Plumbing in St. Louis](https://legacyplumbingmo.com/locations/st-louis) ### Next Steps - [Request Service](https://legacyplumbingmo.com/request-service) - [View All Commercial Services](https://legacyplumbingmo.com/commercial) - [Request a Free Estimate](https://legacyplumbingmo.com/contact-us) Serving the Greater St. Louis Area ## Backflow Prevention & Testing Across the St. Louis Metro Every municipality in the St. Louis area — from St. Louis City and Florissant to St. Peters, Wentzville, and Ballwin — requires annual backflow testing on RPZ and DCV assemblies, and most water districts will shut off service if the report doesn't land on time. Our state-licensed backflow technicians install, repair, certify, and file the paperwork directly with Missouri American Water and the city water districts across the metro — so your assemblies stay compliant and your water stays on. Don't see your city below? We work the entire metro and a 2-hour radius from O'Fallon, MO. [View full service area →](https://legacyplumbingmo.com/service-areas) ### St. Charles County - [O'Fallon](https://legacyplumbingmo.com/locations/ofallon) - [St. Charles](https://legacyplumbingmo.com/locations/st-charles) - [St. Peters](https://legacyplumbingmo.com/locations/st-peters) - [Wentzville](https://legacyplumbingmo.com/locations/wentzville) - [Lake Saint Louis](https://legacyplumbingmo.com/service-area/lake-st-louis-mo) - [Dardenne Prairie](https://legacyplumbingmo.com/service-area/dardenne-prairie-mo) - [Cottleville](https://legacyplumbingmo.com/service-area/cottleville-mo) - [Weldon Spring](https://legacyplumbingmo.com/service-area/weldon-spring-mo) - [New Melle](https://legacyplumbingmo.com/service-area/new-melle-mo) - [Foristell](https://legacyplumbingmo.com/service-area/foristell-mo) ### Lincoln County - [Troy](https://legacyplumbingmo.com/service-area/troy-mo) - [Moscow Mills](https://legacyplumbingmo.com/service-area/moscow-mills-mo) - [Elsberry](https://legacyplumbingmo.com/service-area/elsberry-mo) - [Winfield](https://legacyplumbingmo.com/service-area/winfield-mo) - [Old Monroe](https://legacyplumbingmo.com/service-area/old-monroe-mo) - [Hawk Point](https://legacyplumbingmo.com/service-area/hawk-point-mo) - [Silex](https://legacyplumbingmo.com/service-area/silex-mo) ### Warren County - [Warrenton](https://legacyplumbingmo.com/service-area/warrenton-mo) - [Wright City](https://legacyplumbingmo.com/service-area/wright-city-mo) - [Marthasville](https://legacyplumbingmo.com/service-area/marthasville-mo) - [Innsbrook](https://legacyplumbingmo.com/service-area/innsbrook-mo) - [Truesdale](https://legacyplumbingmo.com/service-area/truesdale-mo) ### St. Louis County - [Affton](https://legacyplumbingmo.com/service-area/affton-mo) - [Clayton](https://legacyplumbingmo.com/locations/clayton) - [Ladue](https://legacyplumbingmo.com/service-area/ladue-mo) - [Brentwood](https://legacyplumbingmo.com/service-area/brentwood-mo) - [Chesterfield](https://legacyplumbingmo.com/locations/chesterfield) - [Crestwood](https://legacyplumbingmo.com/service-area/crestwood-mo) - [Des Peres](https://legacyplumbingmo.com/service-area/des-peres-mo) - [Fenton](https://legacyplumbingmo.com/service-area/fenton-mo) - [Lemay](https://legacyplumbingmo.com/service-area/lemay-mo) - [Maplewood](https://legacyplumbingmo.com/service-area/maplewood-mo) ### Jefferson County - [Arnold](https://legacyplumbingmo.com/service-area/arnold-mo) - [Festus](https://legacyplumbingmo.com/service-area/festus-mo) - [Crystal City](https://legacyplumbingmo.com/service-area/crystal-city-mo) - [Herculaneum](https://legacyplumbingmo.com/service-area/herculaneum-mo) - [Pevely](https://legacyplumbingmo.com/service-area/pevely-mo) - [De Soto](https://legacyplumbingmo.com/service-area/de-soto-mo) - [Hillsboro](https://legacyplumbingmo.com/service-area/hillsboro-mo) - [Barnhart](https://legacyplumbingmo.com/service-area/barnhart-mo) - [Imperial](https://legacyplumbingmo.com/service-area/imperial-mo) - [High Ridge](https://legacyplumbingmo.com/service-area/high-ridge-mo) ### St. Louis City - [Central West End](https://legacyplumbingmo.com/service-area/central-west-end-mo) - [Compton Heights](https://legacyplumbingmo.com/service-area/compton-heights-mo) - [Lafayette Square](https://legacyplumbingmo.com/service-area/lafayette-square-mo) - [Soulard](https://legacyplumbingmo.com/service-area/soulard-mo) - [Tower Grove South](https://legacyplumbingmo.com/service-area/tower-grove-south-mo) - [Shaw](https://legacyplumbingmo.com/service-area/shaw-mo) - [Benton Park](https://legacyplumbingmo.com/service-area/benton-park-mo) - [The Hill](https://legacyplumbingmo.com/service-area/the-hill-mo) - [Dogtown](https://legacyplumbingmo.com/service-area/dogtown-mo) - [South City](https://legacyplumbingmo.com/service-area/south-city-st-louis-mo) For examples of this work, see [Facility Water Heater & Backflow Program (Regional Portfolio)](https://legacyplumbingmo.com/projects/facility-water-heater-backflow-program) . For planning guidance, read [Before the First Hard Freeze: A Plumbing Walk-Through for St. Louis Commercial Buildings](https://legacyplumbingmo.com/resources/first-hard-freeze-commercial-plumbing-walkthrough-st-louis) . ## Need a Backflow Test in St. Louis? Get a certified tester from a self-performing commercial plumbing contractor based in O'Fallon, MO. [Get Free Estimate](https://legacyplumbingmo.com/contact-us) [636-978-0120](tel:+16369780120) ## From Our Job Sites Backflow preventer and booster pump in a mechanical room Commercial water heater with backflow preventer and expansion tank ## Related - [Contact Legacy Plumbing](https://legacyplumbingmo.com/contact-us) - [Company facts](https://legacyplumbingmo.com/company-facts) - [All pages (llms.txt)](https://legacyplumbingmo.com/llms.txt)