Pressure Relief Valve Leaking

brucepirger

I have a Buderus boiler (oil with Riello burner), radiant heat, indirect hot water system, all installed new in 2003. It appears that the pressure relief valve (30psi) mounted on the supply coming off the boiler is leaking. I heard what sounded like cavitation in the primary pump and the system took water (I have the feedline on a valve).

When the boiler fires, the system pressure rises to about 12-14 psi. The expansion tank does not appear to be waterlogged.

Is there any obvious reason why this prv would be leaking so soon? Is the pressure in the system too low?

I also have the "micro air scrubber" in the primary loop...and I can hear it vent when I added the water. I forget the name of the air scrubber...but I remember well it was highly recommended.

I tried to toggle the prv valve in hopes that perhaps I could flush out whatever is causing this leak from the valve seat...it seems like it might have worked...the leak seems to be reduced/gone.

Do these prv's tend to fail "early"? Water and non-toxic antifreeze mix in the system.

No other problems with the system...radiant is incredible...and thanks to all who may remember me from years ago.

Any thoughts/suggestions would be most appreciated. Thanks!

Brad White_185

A small handful of thoughts

First the housekeeping part: I assume you have a Spirovent, good. I assume that you are pumping away from the expansion tank (based on the assumption that you were guided here when the work was done).

Relief valves are among the most reliable devices and have a fairly low failure rate but anything can and will fail.

Some thoughts:

1) Your testing of the valve may have flushed whatever was holding the seat open, but for something to get into that seat took some internal pressure lift I would think. Symptom may be gone, the root problem may or may not be.

2) Your pressure gauge maybe is lying to you and you are reaching 30 PSI+. What is the cold fill pressure? If that too is nearly that range as I would think it might be (12-14 lbs.) and it stays there when heated, I suspect the gauge. Bring it in for questioning.

3) The anti-freeze may be working on the seat material or doing what glycol does best: find leaks. The low surface tension tends to cause oozing out valve stems and other places where you normally do not have leaks with water.

Brad White_185

Oops Double Post NM

brucepirger

Thanks Brad! Yes, Spirovent...that's it. And indeed, pumping away.

The cold fill pressure is 12-14 as you say, and I don't see much variation when it is hot. I'll have to look more closely. Doesn't the air pressure in the expansion tank play into the system pressure in a big way?

The antifreeze is the non-toxic kind...memory seems to tell me it is polypropolene glycol...REM-1.

It is easy enough to replace the prv, it is on a threaded nipple. The only hassle is losing some water/antifreeze mix...though I have ball valves to isolate the majoriy of the system. But as you say, I wonder if there is a bigger issue. I think the temp/pressure guage is right nearby...maybe I should change that too when I'm at it.

Thanks!