Symptoms
- All heads in a zone spray weakly
- Pressure was fine before but has gradually dropped
- Pressure improves noticeably if fewer heads run at once
Likely causes
- CommonToo many sprinkler heads running on one zone for the available flowAdding heads to a zone beyond its designed capacity spreads pressure too thin.
- CommonPartially closed main shutoff or backflow valveA valve not fully open restricts overall system flow.
- PossibleLeak somewhere in the main line before the valvesA leak upstream of the zone valves reduces pressure to everything downstream.
- PossibleClogged main line filter or backflow preventer strainerSediment buildup at the system's filter point restricts flow to all zones.
What to do
- Check that the main shutoff valve and any backflow preventer valves are fully open.
- Clean any filter or strainer at the backflow preventer or main valve assembly.
- Test each zone individually and compare pressure; if all zones are equally weak, suspect a main line or supply issue rather than a specific zone.
- Check your home's overall water pressure isn't independently low, which would explain reduced irrigation performance too.
- Inspect the yard for any wet spots that might indicate a main line leak upstream of the valves.
- If a zone has more heads than the original design intended, consider splitting it into two zones for adequate pressure.
Tools and parts
- None required for basic checks
Backflow preventer strainerSearch: “irrigation backflow preventer strainer”
When to call a pro
An irrigation professional can measure static and dynamic pressure to pinpoint whether the issue is a leak, valve, or zone design problem.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.