Low Pressure on 3 of 5 Zones After Winterization

Post-Winter Startup: Three Zones Weak, Two Normal

Rain Bird system professionally installed and winterized. Zones 1 & 3 work; zones 2, 4, 5 have low pressure (dribble to half-pop). Only 3 main valves for 5 zones ("double up"). One zone 2 head sunk 3 inches.

Diagnostic Priorities

1. Check for mainline leaks — especially near repair areas or sunk head
2. Verify all valve flow controls — adjust: open fully, close fully counting turns, reopen halfway
3. Inspect valve internals — debris from winterization blowout can lodge in diaphragms
4. Investigate "double up" wiring — two zones per valve output can cause pressure issues if both run simultaneously
5. Raise and inspect sunk head — may indicate pipe settlement or break

Zone Doubling Concern

If two zones share one valve output, they run simultaneously. This doubles GPM demand, likely exceeding pump/pressure capacity. Verify controller programming — each zone should have its own valve.