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The thing I am pointing at in the picture is part of our heating system piping. It is mounted on the wall behind the boiler. The blue pipe on the far side is a water supply line. It is to allow the boiler to add more water into the system when needed. If I open the valve to let water flow, the thing I am pointing at eventually starts spraying water all over the place. It just started doing that this year.
Anyone know what it is , why it is leaking and what I need to do to fix it?
I'm not sure what you're pointing at but following the blue pipe the thing on the right is backflow preventer, that will prevent water from making it's way back into the supply if there is more pressure in the boiler than the water line. The second thing on the left is a pressure reducer.
Last edited by thecoalman; 02-06-2013 at 08:08 PM..
Yep, backflow preventer. It's designed so that if it fails, it vents the water out the third opening rather than allow backflow into the potable water system. So it just needs to be replaced. You might also need a drain pipe installed to meet code.
I'll agree with the pressure reduction (limitation) valve as being the object with the dome, but the other looks more like an overpressure relief valve. Note where it is designed to accept another pipe to drain off the water instead of spray it. A check-valve / backflow preventer doesn't need that.
Using terms like that incorrectly bothers me, even when it is a major manufacturer that does it. To prevent backflow, one uses a check valve, which is also known as a backflow preventer. Those devices do NOT have "vents" or anything along those lines. They simply stop the flow of water in one direction, much like a diode in electronics does for electricity.
That valve shown is more accurately a pressure relief valve with one way (undirectional) flow-through or injection for makeup water when the pressure drops below a certain level, as might happen with a collapsing steam pocket.
Using terms like that incorrectly bothers me, even when it is a major manufacturer that does it. To prevent backflow, one uses a check valve, which is also known as a backflow preventer. Those devices do NOT have "vents" or anything along those lines. They simply stop the flow of water in one direction, much like a diode in electronics does for electricity.
That valve shown is more accurately a pressure relief valve with one way (undirectional) flow-through or injection for makeup water when the pressure drops below a certain level, as might happen with a collapsing steam pocket.
Harry as I understand it there is two check valves in it and the vent sits between them, if the boiler side check fails then it will vent.
KB, I'm well aware of that. I don't disagree that you used the common terms for it. It is mislabeled - perhaps the same casting was used in a different application at some point, it makes no difference to me. The PURPOSE of the device is as I stated, injector / relief valve. I once had a science teacher tell me a resistor was a capacitor and a capacitor a resistor. It didn't make it so. I once saw an elevator where some wag had swapped the up and down buttons. The elevator didn't care.
Errors in use of the language can result in dangerous situations. A heating system with only a replacement backflow preventer (because someone went to a plumbing store and asked for one without showing the old one) instead of a pressure relief valve could be an EXTREMELY dangerous situation. See whaddi mean? The important point is the idea of venting or releasing an excess of pressure, whether it be steam or water or orange juice. Take that out of the system and there is a problem.
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