Backflow prevention and testing in Warren, MI

Backflow testing in Warren is a yearly requirement for any business with a testable backflow assembly, and since late 2025 the city has been bringing homes with underground sprinklers into the program too. The test confirms the device between your plumbing and the public supply still stops water flowing backward when street pressure drops or building pressure climbs.

What our backflow prevention work includes

We repair, rebuild, replace and install backflow assemblies and the piping around them. The test itself must come from a tester holding the two credentials Michigan now requires, explained further down, and Warren’s program sheet asks that required installs and repairs go through a licensed plumbing contractor. The work breaks down like this:

• Repair kits for check valves, relief valves and air inlets after a failed test
• Replacement of cracked, frost-split or obsolete assemblies
• New assemblies where a city survey finds an unprotected cross connection
• Relief drains and air gap funnels under RPZ assemblies
• Hose bibb vacuum breakers on outdoor faucets
• Draining a sprinkler PVB for winter and restarting it in spring

When does Warren require a backflow test?

Warren adopted the state’s cross connection rules as City Ordinance Chapter 41-33. Wherever a cross connection exists or could exist, a backflow assembly has to be installed and then tested at three points:

• Right after installation.
• Every year after that.
• Any time the assembly is moved or repaired.

That annual cycle covers commercial and industrial properties, which the Water Division surveys for cross connections. Kitchens with dish and beverage equipment, medical offices with X-ray or lab equipment, plants with cooling towers or boilers, and buildings with fire sprinklers or irrigation nearly always have at least one assembly. See commercial plumbing services and restaurant plumbing for the rest of what those buildings deal with.

Homes are newer to the program. Starting in late 2025, residential underground irrigation systems need backflow testing, with results submitted every five years. The city estimates more than 20,000 Warren homes have these systems, so it split Warren into five areas, one per year. Owners get a letter or door tag and a questionnaire to return to the Water Department at 12821 Stephens. City crews in marked vehicles then do a free inspection of about 15 to 30 minutes, inside and out, and tell you afterward if a device needs installing, repair or testing.

Who can do backflow testing in Michigan?

Since an August 7, 2023 notice from EGLE and LARA, a backflow tester in Michigan needs two credentials: a valid ASSE 5110 backflow tester certification and a plumbing license. The license can be master or journey, or an apprentice working under a master or journey plumber’s direct supervision. Water systems were told to accept reports only from testers who hold both, with the credentials shown on each report.

Before you hire anyone to test, ask for both numbers. The plumbing license can be confirmed on the State of Michigan’s LARA license search under Skilled Trades. Warren’s brochure says the tester sends the report to the Water Division.

Backflow prevention devices and where you’ll find them

Warren’s cross connection permit lists six kinds of protection. They aren’t interchangeable, and the hazard on the downstream side decides which one is allowed.

An RPZ dumps water from its relief port when a check valve leaks, sometimes a lot of it, so it needs a drain or open space below and should never sit in a pit that can flood. A sprinkler PVB has to sit higher than every head it protects.

What the backflow tester inspects

1. 01

   Plan the shutdown

   Testing a domestic water assembly means the building’s water is off for the length of the test, so the timing gets worked out with you. A fire line may also need the alarm monitoring company notified first.

2. 02

   Check the shutoff valves

   Both shutoffs on the assembly have to close tight. A leaking downstream valve can make a good assembly read badly on the gauge.

3. 03

   Gauge each check valve

   A differential pressure gauge goes on the test cocks. Each check valve has to hold the minimum pressure difference the test procedure sets for that device type.

4. 04

   Test the relief valve or air inlet

   On an RPZ the relief valve has to open at the right point. On a PVB the air inlet has to open as pressure falls.

5. 05

   Record and report

   Make, model, size, serial number and readings go on the report, signed with the tester’s credentials, and the report goes to the Water Division.

For businesses, our post on what happens during a yearly backflow test covers the visit from start to finish.

When a backflow assembly fails its test

A failed test usually comes down to rubber and debris. Check valve discs harden and wear, springs weaken, and grit or scale from the water main lodges on a seat so a check can’t close. Warren made 181 water main repairs in fiscal 2025, and each one can send sediment toward the buildings it feeds.

Most failures are fixed by cleaning the internals or installing a repair kit with new discs, seals and springs. An assembly with a cracked body, a housing split by frost, or parts that are no longer made gets replaced. After either repair, Warren’s rule is the same: a certified tester retests the assembly before it counts as passing. New and replacement assemblies also need a Water Division cross connection permit, and the test report has to be in before the inspection is scheduled.

The model plumbing code that Michigan’s code is based on calls for thermal expansion control on storage water heaters when backflow preventers are present, so a new assembly can mean an expansion tank at the heater too. Ask about it when a heater is replaced; see water heater installation.

Protecting a sprinkler backflow preventer through a Michigan winter

Irrigation assemblies live outdoors, and a PVB full of water in January is a cracked PVB in April. The normal January low at Detroit Metro is about 19°F. Before the first hard freeze, close the irrigation supply valve inside the house, open the assembly’s test cocks to drain it, and drain or blow out the zones. Leaving the test cocks partly open gives trapped water room to expand without splitting the body.

In spring, open the supply slowly with the test cocks closed and watch for drips at the bonnet and body. A freeze-damaged assembly often leaks the moment pressure returns.

Why call Plumber in Warren, MI about a backflow device

Our office is at 11355 Stephens Rd, on the same street as the Water Division yard where Warren’s backflow questionnaires go back. One phone line covers homes, rentals and businesses. When a device fails, we find out why before replacing anything, since grit on a seat needs cleaning rather than a new assembly. You get the cost factors and a written scope first, we tell you which Water Division permit applies, and the retest still comes from a credentialed tester whose report goes to the city.

What affects the cost of backflow testing and repair

The test fee is rarely where the money goes. A passing test is a short visit; a failed one adds parts, a permit for any replacement and a second test. These change the total:

• Device type and size. A large RPZ on a fire line takes longer than a small PVB on a sprinkler system.
• How many assemblies the property has, and whether they can be handled on the same visit.
• Access. An assembly in a ceiling, a pit or a crowded mechanical room takes more time.
• Whether it fails. Repair kits, replacement assemblies, the permit and the retest are where costs grow.
• Related work, such as a drain for an RPZ’s relief discharge or expansion control at the water heater.

Last updated October 25, 2026