The Forth Reason

Some boilers have a hot water coil, sometimes called a tank less water heater. Some times a coil will develop a pin hole in it. If this happens it will cause the house pressure to seep into the boiler causing the the relief valve to leak. to test this turn the water to the coil off and see if the pressure stops raising. An indirect water heater. can become defective and cause the same thing as the coil. to test this turn the water to the tank off and see if the pressure stops raising.