Pressure relief valve on boiler is dripping.Starts to drip more when the boiler is turned on.Bad relief valve?
Check The Pressure Gauge Should Be Between 12 to 15 Psi. If it's above That Could be Expansion Tank could be overfilled. Or Feeder .
It could be as easy as a bad relief valve. If it is not, you could be looking at a failed expansion tank or a feed/fill valve that is leaking by. Your system might also just have too much water in it, if that happens, the hotter the boiler gets, the higher the pressure, and it can pop the relief valve. Those are the easy things, if you have a tankless coil boiler, the coil could be leaking, and that would also cause the pressure to increase until the relief valve pops. The easiest things to fix are the system pressure, the relief itself, and the expansion tank and the fill valve(the cheapest too). After checking the system pressure-it should be between 15 to 20 psi on the pressure gauge-I would check the pressure in the expansion tank to see if it is still holding an air charge. It should be 11-12 psi in the tank. The bad news is that the system needs to be de-pressurized to check it, or the tank needs to be removed or isolated from the system(with a valve or some other isolation device). If none of those things do the trick, the coil is the most likely culprit, and will need to be replaced. Good luck
Yes you have a bad relief valve. The reason it drips more when the boiler is on is due to the amount of pressure and flow of water. These units typically dont rust depending upon the material of the housing. But they do fail there are o-rings internally on these relief valves. I would assume that you have an o-ring that is failing.
As a mechanical systems operator I work with industrial boilers on a daily basis. I have to say if in doubt have it tested or replace it ASAP. The safety pressure release valve is your last defense should the boiler over pressure. Our safety valves are required by law to be taken off and sent in to be tested once every three years.
Only to add what Steve said, make sure you have a pipe leading from the Safety valve to the floor, that way if the Safety valve let's go it won't be shooting straight at someone's face or other equipment. If you could, pipe the safety to a drain but by all means leave the line open, Put no other valve in the line to restrict what the safety is meant to do.
