Commercial Backflow Testing & Prevention
Expert Commercial Backflow Testing & Prevention in Seattle, King & Pierce Counties
Protecting the public water supply isn’t just a best practice—it is the law. For commercial properties in Western Washington, backflow prevention assemblies are the critical line of defense keeping contaminated water, chemicals, and industrial waste from reversing into the clean municipal drinking water. Grindstone Guys provides certified backflow testing, repair, and installation for businesses across Seattle, King County, and Pierce County.
We handle the testing, perform any necessary repairs on the spot, and submit all compliance paperwork directly to your local water purveyor so you can stay focused on running your business.
What is Backflow and Why is Testing Required?
Water is designed to flow in one direction: from the city main into your commercial facility. However, a sudden drop in city water pressure (like a burst water main or a fire truck opening a hydrant nearby) can cause back-siphonage. Alternatively, high pressure from your facility’s boilers or pumps can cause back-pressure.
Both events force contaminated water from your irrigation systems, fire sprinklers, or industrial equipment backward into the clean water supply.
Because mechanical backflow preventers contain internal seals, springs, and moving parts, they wear out over time. This is why Washington State law requires annual testing by a certified Backflow Assembly Tester (BAT) to ensure the device is still functioning flawlessly.
Our Certified Backflow Services
Whether you manage a single retail storefront or a sprawling industrial complex, we provide complete lifecycle management for your backflow assemblies:
Annual Backflow Testing
Fast, accurate testing performed by state-certified technicians. We test all makes, models, and sizes of commercial backflow preventers.
Assembly Repair & Rebuilding
If your device fails its annual test, we carry the specialized replacement parts needed to rebuild and repair the internal check valves on the spot, preventing prolonged compliance delays.
New Installation & Upgrades
Expanding your facility or adding a new dedicated irrigation line? We install robust, code-compliant backflow preventers tailored to your specific hazard level.
Automatic Compliance Reporting
We take the administrative burden completely off your shoulders. Once the test is passed, we submit the certified report directly to Seattle Public Utilities, your local King County water district, or Pierce County water purveyor.
Common Commercial Backflow Preventers We Service
Different commercial applications present different levels of hazard to the water supply. Here is a breakdown of the most common assemblies we test and repair:
| Device Type | How It Works | Common Commercial Applications |
| Reduced Pressure Backflow Assembly (RPBA) | Provides the highest level of protection. Features two independent check valves and a relief valve that dumps water if both fail. | High-hazard facilities: hospitals, car washes, chemical plants, and commercial boilers. |
| Double Check Valve Assembly (DCVA) | Uses two spring-loaded check valves in a series. Does not have a relief valve. | Low-hazard applications: standard fire sprinkler systems and indoor commercial plumbing lines. |
| Pressure Vacuum Breaker (PVBA) | Uses a spring-loaded check valve and an air inlet valve to break the vacuum during back-siphonage. | High-hazard but limited to back-siphonage only: commercial landscaping and large irrigation systems. |
Why Choose Grindstone Guys for Backflow Compliance?
Failing to test your backflow assembly can result in severe municipal fines and the immediate shut-off of your facility’s water supply. Grindstone Guys makes compliance effortless.
Our technicians are fully certified by the Washington State Department of Health as Backflow Assembly Testers. We offer automated annual reminders, so you never have to worry about missing a deadline. We also respect your operational hours—we can schedule your brief water shut-off during low-impact times (like early morning or after closing) to ensure your business experiences zero disruption.
Frequently Asked Questions
How long does a backflow test take?
A standard test on a functioning assembly usually takes our certified technicians about 15 to 30 minutes to complete.
Will you have to turn off the water to my building?
Yes, the water flowing through that specific backflow assembly must be briefly turned off (typically for 10-15 minutes) to perform the pressure test. We will always coordinate this with your property manager or facility supervisor beforehand to minimize any disruption to your tenants or daily operations.
What happens if my backflow preventer fails the test?
Do not panic. If a device fails, it usually just means an internal rubber seal has degraded or debris is stuck in a check valve. Our technicians carry rebuild kits for most major brands (like Wilkins, Watts, and Febco) and can often clean or rebuild the device on the same visit. We will then re-test it to ensure it passes.
Do you submit the paperwork, or do I have to?
We handle all the paperwork for you. After a successful test, we will provide a copy for your records and immediately submit the official test report to your local water municipality (e.g., Seattle Public Utilities, Tacoma Water, or your specific King/Pierce County district) to keep you in good standing.
Can you set up an annual testing contract for my property management company?
Absolutely. We partner with numerous commercial property managers and HOAs across the Puget Sound region. We can catalog all the backflow devices across your entire portfolio, track their due dates, and perform the testing automatically each year.