Question about a leaking liquid post

[J2W2]

Hi,

I'm preparing a keg for my latest brew (oatmeal stout). I have pin-lock kegs, and my usual procedure is to:

1. Sanitize everything.
2. Assemble the keg, using keg lube on all the o-rings.
3. Fill the keg with some sanitizer and roll it around to coat everything.
4. Hook it up to a CO2 tank to flush the sanitizer.
5. Fill the keg.

I've had some issues in the past with the poppets on this keg, so I replaced them with universal poppets (first time I've used them). Everything seems to seal up nicely.

As I was flushing the sanitizer out of the keg, it started leaking fairly badly around the liquid post. I checked everything over and noticed that when I look directly down on the post, I can't see the o-ring on the post. The o-rings are pretty new, but I pulled out a replacement and noticed it's slightly larger than the one on the keg. I put the new o-ring on, and it fits a little loose (I can rotate it), but I retested with sanitizer and did not see any leaks. I assume the disconnects compress the o-rings when they are in place.

I can't imagine the universal poppets caused this issue; I think it's the o-rings. Is it better to have an o-ring that shows a little from the top, as opposed to one that's so tight it doesn't show at all? I have an o-ring kit, and the two seem to be only one size apart.

I usually carb my kegs before I put them in my keezer, especially with beers like this that are going on a nitrogen tap (I put them on CO2 arount 8-10 psi). So, I'll have a week to keep an eye on it before it goes in the keezer. I have a short transfer line, and I'm planning to put two disconnects on it and attach it to my liquid line, just to test for any leaks while it carbs.

What are your thoughts?

Thanks for your help!

 

[IslandLizard]

These are the outer o-rings, on top of the post, not the ones under the dip tube flare, right?

I'd say, the problem lies in the o-rings. They're the wrong size or out of spec.

1. The o-ring should fit snug around the "bottom" of the channel. The inner diameter (ID) of the o-ring should be a hair smaller than the inner diameter (bottom) of the channel so it gets stretched a tiny bit, making a seal there. If the o-ring spins its ID is too large, which seems to be your case.
2. The o-ring should project somewhat outside the channel to be able to form a seal when the QD is engaged.
   
3. The o-ring should fit perfectly inside the channel, without leaving (much of) a gap between it and the channel sides. It also shouldn't be too thick, bulging outside the channel. IOW, it has to have the correct CS dimension.
   
4. When the QD is engaged it compresses/deforms the o-ring's cross section (CS), thus forming a seal.

Do you still have some of the old/original ones? Measure (thickness with calipers) and lay on top of each other for ID/OD dimensions. The difference should be obvious.

 

[Tobor_8thMan]

Sometimes the poppets will leak. Simply press down on them (use a screw driver or other narrow object to accomplish) to seal. Or, swap the poppet with another poppet.

 

[J2W2]

These are the outer o-rings, on top of the post, not the ones under the dip tube flare, right?

I'd say, the problem lies in the o-rings. They're the wrong size or out of spec.

1. The o-ring should fit snug around the "bottom" of the channel. The inner diameter (ID) of the o-ring should be a hair smaller than the inner diameter (bottom) of the channel so it gets stretched a tiny bit, making a seal there. If the o-ring spins its ID is too large, which seems to be your case.
2. The o-ring should project somewhat outside the channel to be able to form a seal when the QD is engaged.
   
3. The o-ring should fit perfectly inside the channel, without leaving (much of) a gap between it and the channel sides. It also shouldn't be too thick, bulging outside the channel. IOW, it has to have the correct CS dimension.
   
4. When the QD is engaged it compresses/deforms the o-ring's cross section (CS), thus forming a seal.

Do you still have some of the old/original ones? Measure (thickness with calipers) and lay on top of each other for ID/OD dimensions. The difference should be obvious.

These are the outer o-rings.

1. I also thought that if the o-ring spins, it's too large, but that seems to be the one that isn't leaking.
2. The o-rings that fit snug are the ones that don't seem to project outside the channel, which is why I tried the larger ones.

I don't have calipers, but the OD is obviously larger on the one that can spin on the post than the original ones are.

To err on the side of caution, especially since this is going on a nitro tank at higher pressure, I'm going to use another keg for the stout and then spend some time trying to figure out what the issue is. Unfortunately, this is one of my better kegs (I have a five tap keezer and six "good" kegs I rotate through, and a couple of spares), so I'm hoping to get this figured out.

The universal poppets should not have anything to do with this type of leak, should they? Again, I don't see any leaks until I put the liquid disconnect on? Obviously they act a little differently with the spring sitting on the dip tube, rather that having the three little legs holding them in place inside the post.

Thanks again for the help!

 

[IslandLizard]

The universal poppets should not have anything to do with this type of leak, should they? Again, I don't see any leaks until I put the liquid disconnect on? Obviously they act a little differently with the spring sitting on the dip tube, rather that having the three little legs holding them in place inside the post.

The poppets are valves, sealing the passage. If they don't seal you'd know, beer oozing out or gas leaking, losing pressure when disconnected. Once the QDs are on, the poppets are immaterial, the passage is open.

Some universal springs are too long and fail to be opened by the spring in the QD. No gas goes in or beer comes out. In that case, cut a turn off the bottom (the wide part) of the universal spring.

 

[day_trippr]

Post O-rings (the ones that are visible until you snap on a QD) should be tight enough to be a major pita to pry out to replace...

Cheers!

 

[IslandLizard]

should be tight enough to be a major pita to pry out to replace...

I use a small screwdriver, the "jewelry" type, and flip 'em over the top. Easy peasy. No damage to the o-ring either.