Let me describe this symptom and maybe you guys can give me direction...

I put a beer on tap awhile back.  When I would go to tap a beer on that faucet, I would get air (CO2 I guess), then a lot of foam, then beer.  It was new and it would happen over and over.  It happened with the entire keg until I emptied it last night.  I put a keg of helles in its place and the pour is acting normal.  So it’s the keg, I assume and I’m pointing to the o-ring on the liquid out post.  I looked at it last night but I did not inspect it closely.  I assume it has a nick in it or something and the seal was dodgy and it allowed some air to be pulled into the pour and also allowed for the beer to “fall” into the line so that every time I tapped a beer there was CO2 and foam.  What’s weird is that the beer tasted fine, did not seem oxidized and you might also wonder if my CO2 tank would’ve been emptied quickly if that was the case but the answer is NO.  With the new keg pouring properly I have to assume it was the keg.  Thoughts?

If the out-post O ring were leaking, I’d expect to see beer collecting around the base of the post and maybe running down the side of the keg. Rapid CO2 loss would be more symptomatic of leaky seal on the in post. I’d tear down the keg and pay particular attention to the dip tube and poppet as they’re more likely suspects. If you’re using a floating dip tube, my first guess would be the silicone tubing is too long, causing the inlet to be at surface level’

It’s hard to imagine where the beer in the line went while it wasn’t being tapped.  You didn’t mention any liquid leaks.
Are you using a floating dip tube?  The only thing I can visualize is one of those things getting tilted or something.

Guys, thank you.  Good call on the leak… there was no liquid leaking which I agree is strange.  If the o-ring on the liquid-out post had a nick in it, I agree there should have been beer running down the side of the keg and into the fridge.  I do plan to closely examine the keg and I can check the poppet too.  I have never seen this happen and I have 10 kegs so I feel like something is new here.  I also have to assume it’s the keg since the new beer on that faucet is dispensing properly.  I wondered if there was a kink in the beer line that was making it foam so much but I feel like I have isolated this to the keg itself.

Is the liquid pick up floating or submerged?
There are floating pick ups that don’t work well and draw CO2 and foam.

+1. I have one that is an inferior design compared to the others I have from a different mfr. It would spit and sputter to the point that I simply removed it and reinstalled the hard dip tube in that keg.

+1. I have one that is an inferior design compared to the others I have from a different mfr. It would spit and sputter to the point that I simply removed it and reinstalled the hard dip tube in that keg.

Me to when the beer poured foam I replaced it with the long dip tube. I’ve never had that problem with the Clear Beer Drought System.https://clearbeerdraughtsystem.com But only one time with the floating dip tube.

Could there be a leak in the line or at a connection to create a Venturi effect to draw in O2 but small enough to seal when not being drawn?  Just a WAG…

Sorry… I didn’t answer on the dip tube.  All my kegs are standard.  No floating dip tubes.  I don’t imagine a leak in the line since the new keg is dispensing properly.  As “process of elimination” goes, this seems solid but please advise if anyone thinks I didn’t come to the right conclusion.  Seems like something on the keg.  I plan to look closer at it but still have not done that.  Thanks & cheers beerheads.

Sounds like a post or poppit gasket issue, would be my guess, then.  Good luck with the fix.

I agree.  I do have a lot of spare keg parts so I may just replace the poppet and o-ring.  I will also report back in case the answer is something that will help guide someone in the future.  Cheers and thanks again.

Interesting as, apparently, the nick was responsible for disturbing/releasing CO2 in the liquid. Similar to when we pour soda into a glass with ice.

It was just really strange from the moment I put the keg on tap.  When I pulled the handle there was a blast of CO2 and foam and then a stable pour of foam and eventually beer.  The next time I went for a beer, the same thing would happen.  The beer was not overcarbed.  The fact that there was a blast of CO2 and foam suggested that the beer fell back down into the line which does happen slightly after a session but not DURING a session.  At some point I went out there and it seemed like the collar on the QD wasn’t seated properly… it was UP instead of down and snug so I fixed that and thought “mission accomplished” but no… the rest of the keg poured the same way.

Sorry to read you are still dealing with this problem.

I’ve had similar pours when some debris were in the beer line. I’m a homebrewer and throughly clean my lines every 3rd use. However, after kicking a Raspberry Wheat keg I had similar pour problems. Turns out it was pieces of raspberry in the lines!

What was in the line before the problems appeared?

The problem disappeared as soon as that keg was swapped out.  I also clean my lines regularly and there is never a beer with any solids (fruit, hop bits, etc) although I could see a small chunk of yeast getting lodged in there.  The lines I’m using is the hard plastic stuff (I forget the name) that is very rigid.  Bevflex Ultra or something?  It’s not the soft, pliable line.  But with the issue being gone now I have to assume it’s the keg so I will examine the dip tube, the liquid-out post, the o-ring and the poppet.  Cheers.

I had a keg that would sporadically do the same.  I discovered a pinhole in the pickup tube.  When the beer level was above the hole, perfect pours.  When below, a small amount of CO2 was injected into the line causing foam.

I was going to suggest that this is the problem once Ken said he didn’t use a floating dip tube.