Low Pressure All Zones After Winter: Systematic Diagnosis

After a long cold winter, all zones show very low pressure. The main valve between meter and system was closed all winter. No water rush sound when opening it this spring. Suspected pipe damage but no visible evidence.

Step-by-Step Pressure Testing

1. Install a pressure gauge on a backflow preventer test port (1/4" valve).
2. Close the backflow's downstream valve and open the main supply. Gauge should read ≥40 PSI static.
3. Open the backflow valve—pressure should drop then recover to static.
4. Run a zone—pressure should drop then stabilize within 6–10 PSI of static.
5. If drop >10 PSI: Suspect mainline restriction, meter issue, or valve failure.

Additional Checks

• Test house hose bibb pressure with a gauge. If house pressure drops when irrigation runs, the supply (meter/city) is inadequate.
• The main valve's gate/ball may have disconnected from the stem—requires valve replacement.
• Check for freeze damage: even winterized systems can trap water pockets.