How to Install a New Sprinkler Zone Valve

Valves are the heart of your irrigation system, sitting in their underground boxes and taking the brunt of water pressure and temperature swings. When a zone stops firing or starts weeping water constantly, the solenoid or the internal diaphragm has likely given up the ghost. Replacing one is a straightforward plumbing task that saves a professional service call fee. Done well, a valve replacement is a clean, dry installation that avoids the mess of dirt falling into your pipes. You want a setup that is easy to access and uses unions, which ensures that the next time you need to make a repair, you won't need to cut any pipes. Take your time with the wiring connections, as a loose wire nut buried in an underground box is the number one cause of 'mystery' valve failures.

  1. Depressurize and Expose. Turn off the main irrigation water supply and activate the zone manually at the controller to bleed off remaining pressure. Dig out the valve box carefully to expose the valve and the surrounding pipe connections without hitting the wiring.
  2. Extract the Dead Valve. Use a PVC pipe cutter or a hacksaw to cut the pipe on both sides of the valve, as close to the existing fittings as possible. Try to leave enough straight pipe length to install new coupling fittings.
  3. Thread and Tape Adapters. Wrap the threads of your new adapters with three rounds of Teflon tape in a clockwise direction. Screw the male adapters into the inlet and outlet ports of the new valve by hand, then tighten them just a quarter turn more with pliers.
  4. Cement and Position Unions. Install PVC unions on both sides of the valve; this allows for easy removal in the future. Glue the union tailpieces onto the existing pipe and ensure the valve is oriented correctly according to the arrow indicating water flow direction.
  5. Splice Solenoid Connections. Strip a half-inch of insulation from the valve solenoid wires and the field wires. Join one solenoid wire to the common wire and the other to the zone-specific wire using waterproof grease-filled wire nuts.
  6. Verify and Restore. Turn the water supply back on slowly to check for leaks at the unions. Once dry, run the zone for one minute to verify operation, then pack the soil back into the box.