Rain Bird Rotor Leaking at Bottom of Slope: Low Head Drainage

One Rain Bird rotor leaks at the base (around the rotation adjustment screw) after cycle ends. It's the last head on a zone, on a slight decline. Other heads on other zones don't leak.

Diagnosis: Low Head Drainage

Water remaining in the lateral pipe after the valve closes drains out through the lowest head. The leak at the screw is residual pressure releasing.

Two Fixes

1. Replace with a check-valve rotor: Rain Bird 5000/5500 series with SAM (Seal-A-Matic) or Hunter I-20 with check valve.
2. Install an in-line check valve: Directly under the existing head on the riser.

Option 1 is cleaner; option 2 works if you want to keep the current head.