Pressure relief problem

David Meiland

I recently noticed a bit of water coming out of the pressure relief pipe from my boiler (it drains to paved area where a small water spot has formed). This appears to be a new problem and may be related to a bathroom remodel I just finished.

The house has a 3/4" copper main water line with 1/2" branches. When I installed the heating system 5 years ago, I ran a new 1/2" branch to the boiler board for the makeup line. During the recent remodel my plumber tapped into that 1/2" line and fed the toilet from it (it's the closest supply line to the toilet location). Now, when that toilet is flushed, a slow, temporary drip from the boiler pressure relief happens about 60 seconds later (there's about 20 feet of pipe before it emerges from the crawl space).

The system is a staple-up with two zones and eight loops, and has been working fine since installed. There is a backflow preventer with its own pressure relief, and that doesn't appear to be dripping. Water was bled completely from the hot and cold lines a couple of times during the remodel. The toilet was set last week. There are no other changes I can think of.

Is it possible that the temporary reduction of pressure in the makeup line is somehow causing the pressure relief to open. The toilet flushing and the drip seem very consistently related. The system has about 13 PSI in it and as far as I know the boiler relief is a 30 PSI device. I'm clueless...

John@Reliable_2

I bet .................

that when they drained line they opened relief valve so line / system would drain quicker. Most times when this is done the relief will not seat again.This also will happen 99% of the time when valve is tested.I would ask them to return and replace valve.Most times whenever we touch one it gets replaced. If pressure was your problem the back flow should be the one to leak. Hope this helps John@Reliable

kframe

Could it possibly be a water hammer effect when the toilet fill valve shuts off?

I don't see how, though...

Unknown

If your relief valve drips at 13#

change it.

If your gauge is stuck at 13 and your relief valve is dripping at 30#, you have a problem in your system that developed AFTER the gauge stuck.

An expansion tank problem or a boiler pressure reducing valve problem or a water heater coil problem....

Guy_3

Pressure relief

It sounds to me like the plumber relieved the heating system of it's pressure. When the system re-filled, the feed valve may have gotten debris caught under the seats, causing it to leak by. Or, like relief valves, after years of dis-use, just did not want to be disturbed. Like some people that I know....