Low Pressure on One Zone
If only one zone has low pressure while others are fine, the problem is isolated to that zone — a partially open valve, a lateral leak, or too many heads on the zone.
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Symptoms
- One zone has noticeably weaker spray than the others
- Heads on one zone barely pop up or have reduced throw
- This zone used to work fine but has gotten worse
Diagnosis
The zone valve may not be opening fully, there may be a leak in the lateral line bleeding pressure, or additional heads were added to the zone beyond its GPM capacity.
Step-by-Step Repair
- 1
Run the weak zone and check the zone valve — open it fully manually to see if pressure improves. If it does, the valve diaphragm may be partially stuck.
- 2
Walk the zone while it's running. Look for soggy areas, bubbling, or water surfacing — this indicates a lateral leak.
- 3
Count the number of heads on the zone and calculate the total GPM demand. Compare to your available water supply GPM.
- 4
If the zone is overloaded (too many GPM), you'll need to split it into two zones with a new valve and wire.
- 5
Check the heads for clogged nozzles — a partially clogged head restricts flow and affects the whole zone.
Parts Needed
- •Zone Valve × 1 — If splitting into two zones
- •Sprinkler Wire × 100 — If adding a new zone
Pro Tips
- A good rule of thumb: spray zones should use no more than 75% of your available GPM.
Prevention Tips
- When adding heads to an existing zone, always recalculate the total GPM to make sure you don't overload it.
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