Quick answer: Low pressure on only one irrigation zone usually means the restriction or water loss is specific to that zone. Common causes include a leak, partially opening valve, clogged valve or filter, too many or incorrect nozzles, damaged piping, or multiple failing heads.
Compare the affected zone with the rest
If other zones have normal pressure, a whole-property water-supply problem becomes less likely. Watch whether every head on the weak zone is affected or only a small section.
Common causes
- Underground lateral-line leak
- Valve not opening fully
- Debris or restriction inside a valve
- Broken riser or sprinkler body
- Incorrect nozzle demand for available flow
- Clogged nozzles or filters
What to look for
Run the zone and look for pooling, unusually green or soft areas, bubbling soil, heads that barely rise, or one area that is much weaker than the rest. A hidden leak can lose water before it reaches the sprinklers.
When to call for diagnosis
When the cause is not visible, pressure and valve troubleshooting can help separate a leak from a valve or coverage problem. See sprinkler repair and troubleshooting.
