This is not an interesting topic. However, I couldn’t find what I needed for this little project on Google, so figured I’d create a post that is likely to be found when people are searching for a solution to a leaking relief valve.
Your water heater has a T&P valve, which stands for Temperature and Pressure Valve. This valve opens when temperature and/or pressure exceed a pre-defined threshold. This is a safety feature so that your water heater does not explode if the pressure goes too high. I have a Weil Mclain Superstor indirect water heater and the T&P Valve is on the top, as shown below. It usually is designed to open at 210F and/or 150 psi, which is waaay above the safe operating temperature and pressure of a domestic water heater. Watts is the leading brand of these devices.