[richardt]

Gas is escaping through the relief valve!  Thankfully I didn't blow a whole 5 pound CO2 tank to figure that out. 

I brew 10 gallon batches (last was an American Wheat) and ferment in two 5 gallon plastic buckets.

After primary fermentation is done, I racked to two of my 5 gallon corny kegs.  I closed the lids and pressurized both kegs to well over 40 PSI (could have been as high as 60 psi).

I then removed the gas in QD and put it back on my still-to-be-drained corny keg containing my IPA.  That  keg got drained this weekend at a nice neighborhood party down the street.  So I come back home to get my American Wheat Keg and I spray my StarSan like I always do over the QD's, both posts, and the relief valve.  After connecting the QD's I was amazed to see the bubbles emanating from the relief valve with pressures of just 10 psi.

What is going on here?  Do I need to replace the relief valve with a new o-ring?  Or is the problem more complicated than that?
The beer tastes fine from the keg in question (not infected).

Never one to spoil a party.  I just put the keg back in the fridge and took the other 5 gallon corny back to the party and kept the guests at the party happy.  Just one more reason to brew 10 gallon batches, my friends.

[IHBHS]

Unscrew the relief valve from the lid by leaving it in the closed position and turning it counter clockwise, there is a seal at the end of the assy.  make sure there is nothing caked on it (beerstone) that might prevent it from sealing all the way.  if there does not appear to be any crap caked on it could be the spring just got weak.  you can get replacement stems from foxx equipment co, they're only a few bucks, i will also send a couple of those out since shipping on em is nothing

[tschmidlin]

you can get replacement stems from foxx equipment co, they're only a few bucks, i will also send a couple of those out since shipping on em is nothing

Do you know what page of their catalog they're on?

[enso]

Sometimes it can be as simple as making sure the relief valve is screwed in tightly.  Check that and try it again.

I find with one of my kegs it will leak slightly, but it will stop if I turn the valve a bit.  It probably need to be replaced but so far it has kept pressure.

As IHBHS recommended check for crud.  Another thing to try is once you have pulled the valve out and checked it, put a dab of keg lube on the rubber tip then put it back in.  That helps sometimes.

[gordonstrong]

I just replaced one last night.  I'm done messing around with intermittent leaks. Keep a supply of keg parts around and when you find a leak, swap the part.  If you have a lot of kegs and don't get to all of them frequently, there's nothing worse than finding a great beer oxidized because the keg didn't hold pressure.

Yes, do a cursory quick check to see if it's something obvious (like it not being screwed in sufficiently, or it being clogged by a visible particle of something).  More often than not, you won't see anything like that.

I think it's good practice to clean then store your kegs under pressure. When you need to fill one, check to see if it still held pressure.  If not, move it from the 'ready to use' pile into the 'needs fixed' pile.

[bluesman]

+1

I buy o-rings by the hundred.  Too much time is invested in making beer to compromise it's quality by an o-ring or bad PRV.
I recently started reworking some my kegs that had intermittent pressure issues.  O-rings are fairly inexpensive as opposed to your time and beer costs.

[IHBHS]

I was mistaken it's not Foxx, it's Brewcraft that has those cheap.  It is called a ball lock pressure relief valve # 6006-1 but like i said i'd mail a couple out for next to nothing

[beveragebob]

In a pinch you can unscrew the relief valve and coat the rubber oring, grommet, washer whatever you want to call it with keg lube and retighten and check for leaks.

[enso]

Keep a supply of keg parts around and when you find a leak, swap the part. 

That right there is some excellent advice.  I try to do that.  I just find things break faster than I remember to restock my parts supply! 

Buy in bulk is what you have to do.  Worthwhile investment in sanity.  Unfortunately I have not found a one-stop shop for all parts needed that can be bought in bulk.