Why Backflow Preventers Need Annual Testing in Minnesota

A backflow preventer can look perfectly normal from the outside and still fail when water pressure changes.

That is why Minnesota requires testable backflow prevention assemblies to be tested after installation and at least once each year afterward. Annual testing confirms that the internal check valves, relief valves and air inlets are still capable of protecting the drinking-water supply.

If you received a backflow testing notice from your city or water supplier, it usually means an assembly registered to your property is due for its annual test.

What Does a Backflow Preventer Do?

Water should move in one direction, from the public water supply or private well into the plumbing system. Backflow occurs when water begins moving in the opposite direction.

There are two primary ways this can happen.

Backsiphonage happens when pressure in the water supply drops. A water-main break, heavy water use or firefighting activity can create low pressure that pulls water backward from a connected system.

Backpressure happens when another system develops more pressure than the drinking-water supply. This can push water from that system back into the potable water piping.

A backflow prevention assembly creates a physical barrier between the drinking-water supply and equipment that could introduce contaminated water.

Where Are Backflow Preventers Used?

Testable backflow preventers may be installed on:

• Lawn irrigation and sprinkler systems

• Boiler and hydronic heating systems

• Fire sprinkler systems

• Commercial kitchen equipment

• Chemical dispensing systems

• Water-treatment equipment

• Swimming pool filling systems

• Other equipment connected to potable water

The type of assembly required depends on the possible contaminant and whether the connection can create backsiphonage, backpressure or both.

Why Irrigation Systems Need Backflow Protection

An irrigation system is directly connected to piping buried in the ground. Water around the sprinkler heads can contain soil, fertilizer, pesticides, animal waste and other contaminants.

If water pressure drops while a sprinkler head is submerged or surrounded by contaminated water, that water could be pulled backward into the plumbing system.

Pressure vacuum breakers and reduced-pressure assemblies are commonly used to protect irrigation connections. The correct assembly depends on the design of the system and the hazard involved.

Why Boiler Systems Need Backflow Protection

A boiler fill line connects the drinking-water system to a closed heating system.

Water inside a boiler system may contain corrosion, sediment, treatment chemicals or glycol. It should not be allowed to flow backward into the domestic water piping.

Some boiler installations use a testable backflow prevention assembly. Annual testing verifies that the assembly continues to separate the heating system from the potable water supply.

Because Predictable Plumbing also specializes in boilers and hydronic heating, we understand the complete system surrounding the backflow preventer, not just the assembly itself.

Which Backflow Assemblies Are Tested?

Several types of backflow prevention assemblies can be tested in the field.

RP and RPZ Assemblies

A reduced-pressure principle assembly may be called an RP, RPZ or reduced-pressure-zone backflow preventer.

It contains two check valves with a relief valve between them. If the assembly cannot maintain the required pressure difference, the relief valve opens and discharges water.

RPZ assemblies can be used for higher-hazard connections and systems subject to backpressure.

PVB Assemblies

A pressure vacuum breaker, or PVB, is commonly installed on lawn irrigation systems. It protects against backsiphonage but is not designed to protect against backpressure.

A PVB contains a check valve and an air-inlet valve. Both components are tested to confirm that they operate at the correct pressure.

Double-Check Assemblies

A double-check valve assembly contains two independently operating check valves. These assemblies are generally used for lower-hazard applications.

Both check valves must hold the required pressure for the assembly to pass.

Detector Assemblies

Reduced-pressure detector assemblies and double-check detector assemblies are often associated with fire protection systems. They combine backflow protection with a method of detecting unauthorized or unexpected water use.

Is a PRV a Backflow Preventer?

A PRV and a PVB are different devices.

A PRV, or pressure-reducing valve, lowers and controls water pressure entering a building or plumbing system.

A PVB, or pressure vacuum breaker, is a backflow prevention assembly that protects against backsiphonage.

The abbreviations are easy to confuse. If you are unsure which device is installed at your property, send Predictable Plumbing a picture of the assembly and its identification tag.

What Happens During a Backflow Test?

During a backflow prevention test, a certified tester connects testing equipment to the assembly’s test cocks and measures how its internal components respond to changes in pressure.

Depending on the type of assembly, the test may check:

• Whether the first check valve closes properly

• Whether the second check valve closes properly

• When an RPZ relief valve begins to open

• Whether a PVB air-inlet valve opens correctly

• Whether shutoff valves and test cocks are accessible and operational

• Whether the assembly passes the required performance standards

The water serving the protected system normally needs to be shut off briefly during testing. This does not always require shutting off water to the entire building.

After the test, the tester records the results and updates the assembly’s test tag.

Why Can an Assembly Fail if It Is Not Leaking?

Backflow preventers contain springs, seals, discs and other moving components. These parts can wear out or become obstructed even when there is no visible leak.

Common causes of failure include:

• Dirt caught in a check valve

• Mineral buildup inside the assembly

• Worn rubber discs or seals

• Weakened or broken springs

• A relief valve that opens too early

• A relief valve that does not open

• Leaking or seized shutoff valves

• Freeze damage

• Damage during irrigation startup or winterization

• Long periods without operation

A visual inspection cannot confirm that the internal components are working. Pressure testing is needed to determine whether the assembly passes.

What Happens if a Backflow Preventer Fails?

A failed test identifies which part of the assembly did not meet the required standard. The solution may involve cleaning, replacing internal components, rebuilding the assembly or replacing the complete device.

The correct option depends on the assembly’s condition, age, manufacturer and availability of repair parts.

Repairs are separate from the standard testing service. Any additional work should be explained and priced before it begins. Once the correction is complete, the assembly must be retested to confirm that it passes.

How Often Is Backflow Testing Required in Minnesota?

The Minnesota Plumbing Code requires testable backflow prevention assemblies to be tested:

• When initially installed

• After being repaired

• After being relocated

• At least once every year afterward

• More frequently when required by the local authority

The test must be completed by a certified backflow prevention assembly tester. Minnesota also requires testing and maintenance records to be maintained and submitted to the appropriate authority when applicable.

The Minnesota Department of Labor and Industry requires backflow prevention testers to maintain the appropriate state and ASSE certification.

What Should You Do With a Testing Notice?

If your city or water supplier sends you a backflow testing notice, do not throw it away. The notice may contain:

• The registered assembly information

• A deadline for completing the test

• A city-specific testing form

• An online reporting link

• Instructions for submitting the results

• Contact information for the responsible department

Give the notice to your backflow tester when scheduling. This helps ensure the correct assembly is tested and the completed report is sent to the right place.

Schedule Backflow Testing in the Western Twin Cities

Predictable Plumbing provides certified backflow prevention testing in Minneapolis and throughout the western Twin Cities. We test RPZ, PVB, double-check and other testable backflow prevention assemblies.

We document whether the assembly passes or fails, update the test tag and complete the required testing records.

Learn more about our backflow prevention testing service, call (612) 900-2026 or schedule online.

Predictable Plumbing serves Loretto, Medina, Corcoran, Maple Plain, Independence, Greenfield, Delano, Plymouth, Minnetonka, Maple Grove, Orono, Buffalo, Brooklyn Park, Edina, Minneapolis and nearby western metro communities.