Pressure relief valves are located at the end of pipes.
There is a spring, which under normal pressure conditions, keeps the valve closed.
When pressure inside the pipe builds, the spring releases the valve closure. This, then, allows water to release, and protects the pipes from the damage that would occur if left under pressure.
You never want to repair these valves yourself.
The valves have many smaller pieces inside of the relief valve that could easily get lost when you take it apart. There are necessary steps to follow when disassembling and reassembling the relief valves that are vital to the operation of the system.
If you are not a qualified plumber, you could do something that could result in a faulty relief valve and cause severe damage to pipes.
There is wear and tear on the valve closure. If the pressure relief valves are not properly inspected for wear, serious problems can occur.
The valve closure springs can wear over time and may need to be replaced every 1,000 hours of operation.
If you have a pressure relief valve, you need to schedule regular inspections done by a professional plumber to prevent problems.