Question
What is causing the pressure relief valve on our gas-fired hot water baseboard heating unit to leak?
I know it releases when there's too much pressure in the tank, but what causes that to occur? The valve was excessively releasing water, and we replaced it. Since then, the new one also releases periodically, though much less water and less frequently than before. Wondering if this amount of pressure is due to some other malfunction, and how to correct it, as it had not done anything like that for more than 20 years.
Answer
The pressure relief valve should not be leaking any water. If it is leaking water, there is a problem with the water heater. The most likely cause is a faulty thermostat that is heating the water past the recommended temperature and not shutting off the water heater. This causes pressure to build in the water heater, and the relief valve will open to relieve that pressure. You can install an expansion tank that goes on the cold water line that helps with pressure changes in your water heater. Honestly, if your water heater is 20 years old, you should think about replacing the whole thing.
