Quick answer: Water appearing after the irrigation system turns off can be normal low-head drainage, or it can indicate a valve that is not sealing completely. The key distinction is whether the flow gradually stops or continues long after the zone should be depressurized.
Low-head drainage
Water remaining in lateral piping can drain through the lowest sprinkler in a zone after watering stops. This usually diminishes as the line empties.
Valve seepage
If water continues for an extended period or repeatedly keeps an area wet, the irrigation valve may be allowing water to pass while closed. Debris, a damaged diaphragm or other valve problems can cause seepage.
What to observe
- Which head or zone leaks
- How long the flow continues
- Whether leakage happens even when the system has not recently run
- Whether the area remains continuously saturated
Persistent off-cycle leakage may require irrigation valve repair. For broader system problems, see sprinkler repair.
