Pressure in keg falling off at start

[johndan]

I kegged into a corny this afternoon and after 15-20 minutes it was clear the lid wasn't sealing because the keg wasn't holding pressure. I started at around 2 psi if that's relevant.

After googling some troubleshooting tips, I took off the lid, put it back on without sealing it, and opened up the CO2 to around 15 psi while I rotated the lid around until it seemed to seal. I turned off the CO2 at the tank and the regulator in case I still had a leak. After about two hours the psi has dropped down to 10 psi. I've sprayed the lid and both gas and beer side connections with soapy water and can't see any foaming.

I've never monitored the first few hours of pressure after kegging too closely. If I jacked this up to 15 psi initially to get a good seal, is the beer going to absorb 5 psi of CO2 in a few hours? Or do I still have a leak?

 

[Tobor_8thMan]

Pull up on the lid when closing. Initially hit the keg with at least 30 psi to seal the lid. Check for leaks. If OK, bleed (to purge O2). Hit again with CO2. Put keg into a cold location or keezer and either "burst" carb or set the regulator to the desired levels of CO2.

 

[johndan]

ETA: If I keg the beer at 68F or so, put it on CO2, then drop the temp to 35F in a couple of hours, isn't that going to cause the CO2 to decrease in volume and corresponding a pressure drop? (I had my last physics class in 1981.)

---

Thanks. I did pull up on the lid when closing it, but I only jacked it up to 15 or so. I'll try it again with 30 and see how it goes.

I was puzzled at why I didn't see any bubbles when I sprayed it with dish soap and water, but maybe I missed something. (Well, clearly I've missed something but I'm not sure what yet…)

 

[Tobor_8thMan]

ETA: If I keg the beer at 68F or so, put it on CO2, then drop the temp to 35F in a couple of hours, isn't that going to cause the CO2 to decrease in volume and corresponding a pressure drop? (I had my last physics class in 1981.

Yes, absolutely. CO2 goes into cold liquids easier/quicker than warmer liquids. That's why a "Levels of CO2" chart shows desired psi and temp.

 

[Tobor_8thMan]

It's actually good that you didn't see any bubbles when you did the soap/water check. If seen, this means a leak. If a leak is in the lid usually the follow work. Re-seat the gasket on the lid. Or, rotate the lid 180 degrees and close/seal again.

 

[johndan]

Thanks. Yes, I knew that the beer absorbs CO2 faster at colder temps but I thought a drop from 15 psi to 5 in a few hours was too much.

I’m going to leave it overnight to see if it continues to fall (CO2 turned off in case there really is a leak).

 

[johndan]

If I’m still having issues I’ll try rotating the lid, as you said. I have a couple of spare lids if it comes to that.

It's actually good that you didn't see any bubbles when you did the soap/water check. If seen, this means a leak. If a leak is in the lid usually the follow work. Re-seat the gasket on the lid. Or, rotate the lid 180 degrees and close/seal again.

 

[Tobor_8thMan]

Check the lid gasket and posts. Are the poppets correctly seated?

 

[Tobor_8thMan]

Thanks. Yes, I knew that the beer absorbs CO2 faster at colder temps but I thought a drop from 15 psi to 5 in a few hours was too much.

I’m going to leave it overnight to see if it continues to fall (CO2 turned off in case there really is a leak).

Please realize the gauges are not 100% perfect or accurate. I've had the same happen to me, quick psi reading drop, in a short time, after setting the secondary regulator to the desired psi.

 

[Tobor_8thMan]

I recently had a slow leak in the keg lid. Hmm... checking everything with the water/soap I'm seeing nothing, but I know I'm using more CO2 than usual. Disconnect the CO2, pull the pressure relief and open the lid. I immediately see I didn't properly position the lid gasket. I felt similar to Spock on the 1960's "Star Trek" when Spock was double-checking his work, realized a mistake as says something to the effect he can't believe he missed it!

 

[johndan]

As far as I could tell. Nothing seems misaligned.

Check the lid gasket and posts. Are the poppets correctly seated?

 

[Tobor_8thMan]

Possible a leak is happening somewhere else in the lines between the CO2 tank and the keg? (In other words, it's not a leak in the keg.)

 

[Tobor_8thMan]

Is the tap line connected to the keg when carbonating?

 

[johndan]

No, just the gas line to the keg. I’ll take the lid off tomorrow and inspect it, then rotate it 180.

 

[Tobor_8thMan]

Let me know if any difference once the lid is checked and rotated.

 

[bracconiere]

how's the rubber on the PRV look?

 

[doug293cz]

You need to keep the CO2 turned on when you keg. If you have a "full" keg, you have 5 gal of liquid and about 0.35 gal of headspace. If the CO2 supply isn't on, then the pressure will drop rapidly as the beer absorbs CO2.

Brew on

 

[jerrylotto]

Thanks. Yes, I knew that the beer absorbs CO2 faster at colder temps but I thought a drop from 15 psi to 5 in a few hours was too much.

I’m going to leave it overnight to see if it continues to fall (CO2 turned off in case there really is a leak).

Depends totally on your head space. A full keg might only have a few oz head volume and a drop from 15 to 5 psi woulc correspond to very little CO2 absorption. PV=nRT!

 

[Vale71]

Thanks. Yes, I knew that the beer absorbs CO2 faster at colder temps but I thought a drop from 15 psi to 5 in a few hours was too much.

Beer absorbs CO2 more slowly at colder temps, not the other way around. Even if you don't chill the beer but the beer is not saturated for the temperature/pressure combination you leave it at you will see a pressure drop as beer will still absorb some if not most of the CO2. That's how forced carbonation works, as a matter of fact.

 

[Beer666]

If you have a leak around the posts you should be able to hear it.

 

[johndan]

Pressure was back to zero this morning. On close inspection, the rubber housing on the top of the keg, which I thought was just wrinkled, is pulling away from the keg all along the beer out disconnect.

I’m pressure testing another keg right now and if that holds for a few hours, I’ll transfer the beer to a new one.

how's the rubber on the PRV look?

 

[jerrylotto]

Beer absorbs CO2 more slowly at colder temps, not the other way around. Even if you don't chill the beer but the beer is not saturated for the temperature/pressure combination you leave it at you will see a pressure drop as beer will still absorb some if not most of the CO2. That's how forced carbonation works, as a matter of fact.

Where did you get information about absorption kinetics? More carbon dioxide will dissolve at lower temps (and higher pressures) and the changes are pretty linear, but I'm not familiar with any study of how quickly or slowly absorption occurs.

 

[johndan]

I’ve read so much in the last year I couldn’t tell you—I’m guessing a random, unreliable internet post. But, yeah, in retrospect I know enough about physics to realize you must be right. Same reason the relative humidity in the winter is so low.

- Johndan

Where did you get information about absorption kinetics? More carbon dioxide will dissolve at lower temps (and higher pressures) and the changes are pretty linear, but I'm not familiar with any study of how quickly or slowly absorption occurs.

 

[NSMikeD]

Pressure was back to zero this morning. On close inspection, the rubber housing on the top of the keg, which I thought was just wrinkled, is pulling away from the keg all along the beer out disconnect.

I’m pressure testing another keg right now and if that holds for a few hours, I’ll transfer the beer to a new one.

that should do it. If not. .....

I had the same problem. He’s referring to the pressure relief value. It should have a very small rubber gasket. I unscrewed mine and tada the gasket was missing . Swapped it with one from another keg and leak was gone.

 

[NeoBrew]

From the sound of it you might not have any leak at all. It could just be the beer absorbing it.

 

[VikeMan]

I've never monitored the first few hours of pressure after kegging too closely. If I jacked this up to 15 psi initially to get a good seal, is the beer going to absorb 5 psi of CO2 in a few hours?

That's exactly what I'd expect.

Or do I still have a leak?

Probably not.

Pressure was back to zero this morning. On close inspection, the rubber housing on the top of the keg, which I thought was just wrinkled, is pulling away from the keg all along the beer out disconnect.

That shouldn't cause a leak, unless whatever caused the rubber to pull away also cracked a weld or something. "Zero" (on a typical gauge) is about what I'd expect after sitting overnight.

 

[Vale71]

Where did you get information about absorption kinetics? More carbon dioxide will dissolve at lower temps (and higher pressures) and the changes are pretty linear, but I'm not familiar with any study of how quickly or slowly absorption occurs.

It's called Fick's law of diffusion. Its formulation dates back to 1855, so nothing new really.

 

[Joggin]

Are you using keg lub? Use very little, thin coating on posts and lid gasket as well. Spray with sanitizer to check for leaks anytime you may touch posts after connecting.
Keg Lube - 1 oz | MoreBeer

 

[VikeMan]

Are you using keg lub? Use very little, thin coating on posts and lid gasket as well. Spray with sanitizer to check for leaks anytime you may touch posts after connecting.
Keg Lube - 1 oz | MoreBeer

Keg lube is great for making components slide on and off easier, and preventing tearing of O-rings that could otherwise cause leaks. But it doesn't really fix leaks. I replace all my O-rings frequently (mostly for sanitation purposes) and don't bother with lube anymore.

 

[johndan]

Thanks to everyone for the troubleshooting and general straightening up of some of my misinformed ideas. It looks like the original keg is now holding pressure. I didn't take a scientific approach to this so I can't determine exactly what fixed it, but I think NeoBrew might have been correct when they suggested that I might not have a leak; the pressure dropping 5 psi in a few hours on a new keg might be within normal. Because I turned off the CO2 at that point, the beer just continued to absorb CO2 overnight until the pressure was zero. Normally, I wouldn't have shut off the CO2 so I wouldn't have noticed how much the beer absorbed at the start. My panic was due to the fact that the first time I kegged on CO2 about six months ago, I had a leak and ran the tank dry. When I was kegging this weekend and thought I might have a leak, I knew it was going to be at least a week before I could make the two-hour round trip to the welding shop where I get my canisters refilled.

Of course, since I panicked after that initial fast drop by turned off the CO2; took the keg apart and checked all the connections; swapped out the posts, poppets, and lid; and re-applied keg lube, and more, I'm not completely sure which, if any of those, changed the situation or if there really wasn't a leak in the first place.

Anyway, I appreciate all the insight. Problem solved and I learned a few new things. On to my next misadventure.