Water at the lowest head after watering, a zone that will not shut off, or a puddle at the valve itself. How to find which one you have, with repair steps from Rain Bird and Hunter.
Get a Free Irrigation EstimateA leaking sprinkler valve is usually one of three problems: low head drainage, where water left in the pipe drains out the lowest head after the zone shuts off; debris or a worn diaphragm that keeps the valve from sealing; or a leak at the pipe threads or the bonnet. Low head drainage is fixed with a check valve. A valve that will not seal usually needs its diaphragm cleaned or replaced.
Hunter puts it plainly: there are two reasons a sprinkler will leak water when the system is supposed to be off, and the most common one is low head drainage (Hunter support). The other is the valve. The steps below come from Rain Bird’s Troubleshooting and Maintenance Guide for Residential Automatic Valves (Rain Bird valve guide) and Hunter’s support page, so you can match what you see to the right fix.
If a zone will not shut off, Rain Bird’s guide (section 3-A) works through it in this order:
This also tells you where the problem is. If unplugging the controller stops the water, the controller is the likely cause. If water keeps running with the controller unplugged, it is the valve. Controller shut-off steps for Rain Bird and Hunter models are in our guide on how to turn off sprinklers.
| What you see | Likely cause | Fix |
|---|---|---|
| Water trickles out the lowest head for a while after the zone shuts off, then stops | Low head drainage: the pipe emptying downhill | Check valve at the head or on the line (Hunter HCV, Rain Bird SAM) |
| Heads on one zone keep weeping or running while the zone is off | Valve not sealing: debris on the diaphragm, a clogged or torn diaphragm, or a blocked bleed port | Flush, then clean or replace the diaphragm |
| Water at the valve itself, at the pipe threads | Leaking threaded joint | Tighten; use PTFE tape only |
| Water between the bonnet (cap) and the valve body | Diaphragm not seated, or loose bonnet | Check diaphragm seating, tighten bonnet screws, else replace |
Sources: Rain Bird valve guide sections 4-D, 7-A and 7-B (Rain Bird) and Hunter’s leaking-valve support page (Hunter).
Rain Bird’s guide (section 4-D) gives a simple test for a soggy spot at the lowest head:
Hunter’s fix for low head drainage is the same idea: check valves on the sprinklers or laterals, such as the Hunter HCV (Hunter). It shows up where a zone runs downhill, since water left in the pipe runs to the lowest point.
Before you take a valve apart, try flushing it. Rain Bird’s flush step: turn the bleed screw counter-clockwise only 1 turn, flush one minute, then turn it clockwise to close (Rain Bird valve guide). If the valve still leaks, open it up. These are Rain Bird’s disassembly steps:
Hunter’s support page covers the same two causes. For low head drainage, add check valves. If the zone valve is the cause, Hunter says to disassemble the valve, rinse all the parts with clean water, and re-assemble the valve, and to replace the diaphragm if it is damaged. Debris on the diaphragm is the most common reason a valve will not seal (Hunter support). As with Rain Bird, get the model off the valve before ordering parts.
California homes commonly use anti-siphon valves, and Rain Bird’s guide says they must be installed upright, at least 6 inches above the highest sprinkler head they serve. That puts the valve bodies above ground. Rain Bird notes that in-line valves installed below ground are less likely to incur freeze damage than above-ground models (Rain Bird).
That matters here. NOAA normals show about 54 nights a year at or below 32°F at Victorville and about 70 at El Mirage (NOAA NCEI), and water expands about 9% when it freezes (USGS). The City of Hesperia lists irrigation control valves among the pipes at risk and suggests an insulated cover over them, such as a wooden box lined with insulation (City of Hesperia). After a hard freeze, check valve caps and bodies for cracks before you turn the water back on. How to protect them is in our guides to winterizing sprinklers and backflow freeze protection.
Rain Bird’s guide says a leak between the bonnet and body that does not stop after you reseat the diaphragm and tighten the bonnet means the valve should be replaced. A cracked body or bonnet is also a replacement. So is an old valve where parts for that model are hard to find.
If you have several old valves, it can make sense to rebuild the whole manifold at once. That is a job Monarch’s irrigation team does, and our irrigation cost guide covers what goes into it. The High Desert irrigation guide has the rest of the basics, and our sprinkler timer guide covers the controller side.
Usually it is low head drainage. Water left in the pipe drains out the lowest head, and it stops once the pipe is empty. Hunter calls this the most common reason, and a check valve fixes it.
The valve is not sealing. Debris on the diaphragm is the most common cause, according to Hunter. Flush the valve, then clean or replace the diaphragm.
Rain Bird says at least 6 inches above the highest sprinkler head it serves, installed upright.
Unplug the controller. If the watering stops, the controller is the likely problem. If water keeps running, it is the valve, according to Rain Bird’s troubleshooting guide.
Yes. Water expands about 9% when it freezes, according to USGS, and Rain Bird notes above-ground valves are more likely to freeze than in-line valves installed below ground. Check valve caps and bodies for cracks after a hard freeze.
We checked every number on this page against the public sources below. If a rule or date changes, the agency page is the final word.
Monarch repairs and replaces sprinkler valves and manifolds across the High Desert, and converts spray beds to drip. Get a free estimate and a straight answer on whether your valves need a part or a rebuild.
Get a Free Irrigation EstimateOr call (760) 792-7627
