Reasons why my pressure relief valve leaks?

GNO

I have a Weil-Mcclain EGH steam boiler and the ASME pressure relief valve (rated 15psi) just started leaking. The pressure relief valve in only 2 years old. The pressure gauge reads 1 psi.

Any suggestions? Thanks! 

Jean-David Beyer

I am just a homeowner.

It is remotely possible that your pressure relief valve is defective and needs to be replaced.

There are a few more possibilities..



This is, however, a life-safety problem, so I suggest getting a suitable hot water heating professional in there to see what is going on and to fix it.

Jamie Hall

Steam?

Really?  And the pressure relief is leaking?



Turn that puppy off and get a professional in there to find out why.  The pressure relief valve is the last line of defence before truly catastrophic problems can happen, and should never, ever even crack a drip unless all the other safety devices on a steam boiler have failed.



Not to mention -- if the possibility of the boiler blowing isn't enough -- if the pressure is really that high, you stand a good chance of damaging any vents or traps in the system.

Brad White

If in doubt

go with Jaimie's advice and turn it off.



Frequently, weeping can occur with the tendency to "test" the relief valve under pressure, OR you may have had a runaway condition you were not aware of.  Does your gauge go to zero? If damaged, that may be a sign of an incident.



Either of those can loosen a bit of scale or rust during the discharge which comes to rest on the seat, enough to cause a leak. It may be that simple, but again, it may not. Replacing the valve (and conducting discharge piping downward to a safe place), is short money.



Speaking of pressure gauges, there is a nice part in the MA large boiler code which is out of ASME, I believe. It requires a tee and petcock or isolation valve just below the primary pressure gauge and above the siphon/pigtail. The purpose is to allow you to hook up a temporary gauge of known accuracy and condition, to check the "house gauge". I am not sure if the residential code requires it, but I am going to make it a standard detail. Short money and it can answer a few of your questions now. But not with a hot boiler.