Case 1: Just a Drip
The discharge port releases water from the upper valve chamber to remove pressure while keeping the valve closed. The discharge port may drip when debris is in the chamber, keeping the diverter from fully closing.
Flushing the system may help remove debris from the upper chamber that may be preventing the system from maintaining a good seal around the discharge output.
If flushing the system does not fix the slow-drip leaking discharge, the dome may need to be replaced.
Case 2: Steady Stream
If the upper and lower chamber diverter tubes are mixed up when installing or exchanging a dome, a steady stream of water could leak from the discharge port while the water pressure is charged.
To fix the problem, swap the tubing to the correct ports.