This is unusual. The first thing to ask is what is the water pressure reading at your location? It could be too high. That would cause the valve to be close to opening and leak. The second could be something to do with the thread area that the valve screws into. What is the age of the heater and has it ever been dropped or damaged? Third is how hot is the water temp?
Answers & Comments
This is unusual. The first thing to ask is what is the water pressure reading at your location? It could be too high. That would cause the valve to be close to opening and leak. The second could be something to do with the thread area that the valve screws into. What is the age of the heater and has it ever been dropped or damaged? Third is how hot is the water temp?