Backflow Preventer Failing Its Annual Test — Diagnostics

A failed annual backflow test means the assembly did not hold the pressure or relief conditions required to keep irrigation water out of the drinking-water supply. First identify whether the failure is a continuous leak, a check that will not hold, or damage from freezing.

Symptoms to compare

• Water discharges from the relief port while irrigation is off.
• The tester reports a failed check or differential-pressure reading.
• The body, test cocks, or shutoff valves show cracking or corrosion.

Free diagnostic checks

1. Record which test position failed and the tester’s exact reading.
2. Observe the relief port with the system idle and while one zone runs.
3. Inspect the bonnet, discharge, test cocks, shutoffs, and visible freeze damage.

What the result usually means

• Debris or a worn check seat prevents a check from sealing.
• Partially closed or damaged shutoffs distort the pressure relationship.
• Freeze damage can crack internal or external parts.

Free diagnosis boundary. Backflow devices protect potable water. Stop for a cracked assembly or a regulated test and use a certified backflow tester. Use the matching Repair Guide for the protected repair procedure, parts list, testing, and verification.