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I use pin lock kegs, and until now all of them have been Firestone/Spartanburg. I recently received a Cornelius brand three-gallon pin lock keg. The post threads on this keg are different from all the others, and so are the poppets. The ones that are installed look like this.

The problem I have is that if I only place a single o-ring on each dip tube, the posts leak from underneath. The posts just screw right on with no resistance, and it doesn't create a seal with the dip tube o-ring. I have to have two o-rings on each dip tube to create the seal. (I noticed there were two o-rings when I disassembled it to clean it.)

Is this normal? It really seems like the poppet is just too short. I've found this poppet, which is 1/8" inch taller than the ones that it came with. It says it is for a Cornelius Type 'R', but I don't know if that's what I have.

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The diptube touches the bottom maybe becoming taller than it would be? Things like this could happen when disassembling a lot of kegs and then mismatching parts. If it don't touch the bottom offering resistance and you have problems like this, maybe the poppets are too old and the springs are weak. Putting 2 o-rings will let them more pressurized and prevent leaks, but in the poppet-post place itself. If the leaks are happening between post and keg body and the diptube is not touching the bottom, then your posts are wrong, they probably were from other kind of keg. There's cornelius, spal, firestone... Some posts will be taller than others, and maybe you have a post taller than the keg thread, so you screw all you can and the post still don't reach the keg thread, and only using 2 o-rings it will be ok. But if it works like that, then everything is ok and you don't need to worry. Are you using new o-rings? The old ones could be to dry or deformed and don't will help. If you don't understand anything let me tell, maybe it's just my bad english. Good luck.

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    Thank you for your thoughts. The dip tube definitely is the correct size, and the o-rings are brand new cross-profile ones. (The situation is the same with the normal round o-rings.) What you say about the post being taller than it should is exactly what it feels like. Almost like it's missing a mysterious "plastic insert" that I've seen references to. But, as you say, as long as it holds pressure I guess I shouldn't worry about it. – bughunter Aug 12 '15 at 18:33
  • Reading my answer again, and I don't was clear about telling that one of my kegs used to have a leaking post-poppet that I've fixed with 2 o-rings. The situation of a weak poppet spring I was telling. Just fill it to the mark with water and pressurize it to carbonation levels to check if it holds the pressure before trying with beer! cheers! – jards Aug 12 '15 at 18:53
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Double O-rings seems to be a common thing. One of my cornies has them where a square ring should be (square cross section, but still a circle). A taller poppet could help, if it fits inside the post.

---additional answer:
Keep in mind that these O-rings are making two seals: tube to keg, and tube to post. If the threads in the post are much deeper than threads on the keg, you'll have to stack up more rubber to reach sealing surface in the post. I suspect that you could cut off a short section of rubber tubing to recreate the original style of seal, if you have tubing of a suitable material.

  • OK, at least someone else out there has seen this. I happened to find one of those taller poppets I linked to above at home. Using that poppet, it did seem to seal, but it was still suspicously easy to screw the post all the way down. I didn't trust it so I just decided to stick with the doubled-up o-rings. – bughunter Aug 12 '15 at 18:37
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On many pin lock kegs that I own I have discovered these garbage poppets. The only difference is that mine were white instead of yellow, but they are still number "2"s matching those in your picture. Personally I threw them all out because after taking them out of the posts I was not able to fit them back in. I was able to do this with the longer number "3"s.

I started using universal poppets for both of my firestone and corny pin lock kegs. The upside is that these poppets also depress much easier as they offer considerable less resistance and disassemble much easier, coming out of the post without any work.

You can buy them for very cheap straight from China using Aliexpress.

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