Sprinkler System Repair: Heads, Valves, Lines, and Winterization

How Sprinkler Systems Work

A timer/controller sends an electrical signal to solenoid valves in a valve box. Each valve controls one zone — a section of pipe with multiple sprinkler heads. When the valve opens, water pressure pushes the heads up and they spray. When it closes, the heads retract.

The main water supply enters through a backflow preventer (the above-ground assembly near the house or meter). From there, the mainline runs to the valve boxes. From each valve, lateral lines run to the individual heads in that zone.

Knowing this layout matters for diagnosis. If one head is broken, the problem is local. If an entire zone is not working, the problem is the valve or the wire running to it. If nothing works, the problem is the controller, the main water supply, or the backflow preventer.

Replacing a Broken Sprinkler Head

Turn off the system. Dig around the broken head to expose the riser (the threaded pipe fitting connecting the head to the lateral line). Unscrew the old head counterclockwise.

Take the old head to the hardware store to match the type: pop-up spray heads for small areas, rotor heads for large areas. Match the nozzle pattern (quarter circle, half circle, full circle) and the radius. Installing the wrong head wastes water and leaves dry spots.

Wrap the riser threads with PTFE tape. Screw the new head on hand-tight plus a quarter turn. Set the head to the correct spray pattern and arc. Backfill the soil, packing it gently so the head sits at grade level — too high and it gets clipped by mowers, too low and soil blocks the spray.

Run the zone to test. Adjust the spray arc and distance using the screw on top of the head (turning it clockwise usually reduces the radius).

Finding and Fixing a Leaking Pipe

Symptoms: a soggy area in the yard when the system is off, unexplained high water bills, or a zone that runs but with low pressure at all heads.

Turn on the suspect zone and walk the line looking for water bubbling up from the ground. The leak is usually within a few feet of the wet spot, upstream of the water flow.

Dig carefully to expose the pipe. PVC lateral lines crack from freeze damage or shovel strikes. Poly (black flexible) pipe splits at fittings or gets punctured by roots.

For PVC: cut out the damaged section with a hacksaw. Use two slip couplings and a replacement piece of the same diameter pipe. Prime and cement all joints with PVC primer and solvent cement. Let it cure 30 minutes before turning the water back on.

For poly pipe: cut out the damaged section. Insert barbed couplings into both cut ends and secure with stainless steel clamps. Poly repairs are faster than PVC because there is no glue cure time.

Valve Troubleshooting

A valve that will not open: check the solenoid first. Manually turn the solenoid a quarter turn counterclockwise — if water flows, the solenoid is fine and the problem is the controller or the wire. If no water flows, the valve diaphragm is stuck or the water supply is off.

A valve that will not close (zone keeps running after the controller shuts it off): the diaphragm is torn or debris is stuck in the valve seat. Turn off the main water. Unscrew the valve top, remove the diaphragm and spring, clean the seat, and inspect the diaphragm for tears. Replace if damaged — diaphragm kits cost $5-10.

A valve that weeps (slow trickle from heads even when off): same cause as above, just less severe. Clean the valve or replace the diaphragm.

Controller and Wiring Issues

If a zone does not run from the controller but works when you manually open the valve: the problem is the controller or the wire between them.

Check the controller display for error messages. Test the zone terminal with a multimeter — you should read 24-28V AC when the zone is programmed to run. If no voltage, the controller zone output has failed.

If the controller outputs voltage but the valve does not open, the wire is broken. Sprinkler wire is direct-burial and gets cut by shovels, edgers, and root growth. A wire locator or toner can find the break without digging up the whole run.

Replacement wire: use direct-burial rated sprinkler wire (18 AWG is standard). Splice with waterproof wire connectors designed for underground use — not electrical tape, which fails in wet soil within months.

Winterization

In climates where the ground freezes, water left in the pipes cracks PVC and destroys valve diaphragms. Blow out the system with compressed air before the first hard freeze.

Shut off the main water supply to the sprinkler system. Open the drain valves if your system has them. Connect an air compressor to the blowout fitting (usually a quick-connect or hose bib on the mainline after the backflow preventer).

Set the compressor to 50 PSI maximum for PVC systems (80 PSI max for poly). Run each zone from the controller while the compressor supplies air. Each zone needs 2-3 cycles until no more water comes out of the heads.

Do not exceed the pressure rating. Over-pressurizing melts rotor gears and blows out diaphragms. A 10-gallon compressor at the right pressure is better than a big compressor at too-high pressure.

Tools for Sprinkler Repair

Round-point shovel and hand trowel for digging. PVC cutters or hacksaw. PVC primer and cement. PTFE thread tape. Replacement heads, risers, and couplings matched to your system. Multimeter for checking controller voltage and wire continuity.

For winterization: air compressor capable of sustained 50 PSI output (a small pancake compressor works for most residential systems), blowout adapter fitting for your system type.

Frequently Asked Questions