Backflow Preventer Testing in Davidson County: What Homeowners Need to Know

If you have irrigation, a pool, or a commercial-style hookup at your Nashville home, the backflow preventer protecting the public water supply is your responsibility.

What a Backflow Preventer Does

A backflow preventer is a one-way valve assembly that keeps water from flowing backwards into the public supply. Normally water moves from the city main into your house. Under certain conditions — a fire hydrant being opened nearby, a water main break, a pressure drop — that flow can reverse, and any water sitting in your pipes can be sucked back out into the municipal system.

If the water at your house has been mixing with lawn fertilizer in an irrigation line, or pool chemicals through a fill connection, that contaminated water can end up in your neighbor's drinking glass. The backflow preventer is what stops that.

Where You'll Find Them

Common locations on Nashville residential properties:

• Irrigation system supply — usually a Pressure Vacuum Breaker (PVB) or Reduced Pressure Zone (RPZ) device at the irrigation tie-in.
• Pool fill lines — if your pool has a dedicated fill, there should be a backflow device in the line.
• Fire sprinkler systems — required on any home with a dedicated fire sprinkler.
• Boiler systems — if you have a hydronic heating system that ties into the water supply.
• Commercial-style additions — outbuildings with commercial use, restaurant-style kitchens, etc.

What Metro Water Requires

Metro Water Services in Davidson County requires annual testing on backflow assemblies serving the categories above. The test must be performed by a certified backflow tester, and the results submitted to Metro Water.

If you don't submit a test result, Metro can send a non-compliance notice and ultimately interrupt service until the test is completed.

What a Test Actually Involves

A backflow tester arrives with a calibrated test kit. They isolate the assembly, connect gauges to the test ports, and run a sequence that verifies each check valve and relief valve in the device works at the required pressure differentials.

The test takes about 20 minutes for a typical residential PVB or RPZ. If the device passes, the tester signs off on the form and submits the result. If it fails, repair or replacement parts are needed before a retest.

Common Reasons Assemblies Fail

• Debris in the check valves from line construction or pipe replacement upstream.
• Worn rubber components — the rubber discs and seals harden over years and stop sealing fully.
• Freeze damage — PVBs are particularly vulnerable to freezing because they sit above grade.
• Tampering or upstream modifications that allowed dirt to enter.

When Repair vs. Replace

Most failed residential backflow assemblies can be rebuilt with a kit — new internal seals, springs, and discs. Rebuild kits run a fraction of the cost of a new assembly.

Replacement is the right call when:

• The body itself is corroded or cracked.
• The assembly is more than 15-20 years old.
• The model has been discontinued and parts are unavailable.
• The home is being upgraded to a different irrigation system that needs a different device class.

Winter Care for PVBs

Pressure Vacuum Breakers sit above ground and are the single most common backflow assembly to freeze and burst in a Tennessee winter. Before the first freeze:

• Turn off the irrigation shut-off valve upstream of the PVB.
• Open the PVB test cocks and bleed the assembly fully.
• Wrap the device with insulating cover and a freeze blanket.

A burst PVB in February turns into a flooded yard and a non-compliant assembly all at once.