|It's likely the rotor leaks water because of the "drool" from the nozzle. As the screw diffuses the stream, a little of the water runs down the front of the nozzle turret and into the open area, and it then drains out of the hole in the riser. To prevent it from happening, simply back off the radius reduction screw so it doesn't diffuse the nozzle so much. If the water comes out of the hole in a "stream-like" manner, then it's likely that one of the internal seals is contaminated with debris, so the head will likely need to be replaced.||
Note: Clear model used for demonstration purposes.