Main Line Leak
A main line leak causes significant water loss and often creates a geyser or large flooding area. Main line pipes are always under pressure, so leaks are active anytime the water supply is on.
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Symptoms
- Water bubbling up or flooding an area even when no zones are running
- Significant drop in water pressure across all zones
- Wet area or sinkhole in the yard near the main line path
Diagnosis
A crack, break, or failed fitting in the main (pressurized) supply line between the water source and the zone valves.
Step-by-Step Repair
- 1
Shut off the main irrigation water supply immediately to stop the leak.
- 2
Locate the leak by looking for the wettest area. Dig carefully to expose the pipe.
Call 811 before digging to locate utility lines. - 3
Once the damaged section is exposed, cut out the broken piece with a pipe saw, leaving clean square cuts on both ends.
- 4
Measure the gap. Cut a replacement piece of Schedule 40 PVC pipe to fit, accounting for the depth of the coupling sockets.
- 5
Dry-fit the repair section with two couplings. If there's no flex in the pipe to insert a rigid section, use a telescoping repair coupling (compression coupling) on one end.
- 6
Prime and cement all joints. Allow the cement to cure for the time specified on the can (usually 15-30 minutes before pressurizing).
- 7
Turn the water back on slowly and check for leaks at each joint.
- 8
Once verified, backfill the trench and compact the soil.
Parts Needed
- •Schedule 40 PVC Mainline Pipe × 1
- •PVC Coupling × 2
- •PVC Primer & Cement × 1
Pro Tips
- Telescoping repair couplings save a lot of frustration — they let you make repairs without digging out extra pipe for flex.
- If the main line is old galvanized steel, consider upgrading the damaged section to Schedule 40 PVC with a transition fitting.
Prevention Tips
- Winterize your system before the first freeze by blowing out lines with compressed air.
- Avoid planting trees near the main line path — root intrusion causes cracks over time.
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