Most of us don't even know what a TRP valve is. Let alone what piping should be connected to it. Well, TPR stands for "temperature pressure relief" and there should be a TPR valve on every water heater installed. This valve allows for pressure to be relieved if the water heater somehow malfunctions and the pressure inside the tank reaches unsafe levels. Here is where the problem starts.

The piping that directs the released water should be made from specific materials. PVC is NOT an allowable material for doing this. Copper, CPVC and PEX is allowed. Take a look at your piping coming from the TPR valve that is located either on the top of the water heater or the side near the top and determine if the piping is one of the allowed materials or PVC. If it is PVC, replace it with the approved material.