Pressure relief valve issues on American water heater

I agree with the previous post. Thermal expansion tank is mandatory on the closed heating systems. If you don't have one, nothing can controlled the excessive pressure within your electric water heater, so your TPR valve opens and leaks.

Or, you might have a back-flow valve water which doesn't allow the discharge of the overheated water from inside the water heater tank out. So thermal expansion tank has to be used.

Also check the pressure on the incoming cold water supply. You might have to install a pressure reducing valve.

When water is heated in a closed system it expands and creates pressure. Your t&p; valve is set to release pressure @ 150lbs. psi. To prevent thermal expansion install a thermal expansion tank on your cold water line above your water heater at least 18 ins away but no more than 10ft. Pump the air bladder up to static water pressure. Good luck.