Fixing Pipe Hammer and Leaks at the Backflow Preventer

Why Pipes Shake and Backflow Leaks

Water hammer and leakage at the backflow preventer's relief port usually indicate excessive flow velocity caused by a supply line larger than the valve inlet or downstream piping. The sudden pressure changes make pipes rattle and force the backflow's poppet open, dumping water.

Solutions to Try

1. Throttle the supply gate valve: Partially close the isolation valve before the valves to reduce flow velocity.
2. Adjust valve flow controls: Open each valve's flow control stem fully, then back off just until the valve still closes reliably.
3. Install a pressure-reducing valve (PRV): If the above don't work, a PRV on the irrigation mainline stabilizes pressure and eliminates hammer.

Check the Backflow Preventer

Ensure the backflow device is the correct type for your hazard level and installed at least 12″ above the highest head. A leaking relief port during operation often means the device is doing its job—preventing backflow—but the system pressure is too high or fluctuating violently.