Keg Losing Pressure, No Obvious Leaks

[Docod44]

I have a 3 gallon keg with about 2 gallons of ale that loses pressure throughout the week and I'm at a loss about what to do. I turn off my CO2 tank and disconnect the gas line on Sunday night so that I don't drink during the week but when I reconnect it and turn the pressure back on Friday night, the headspace is clearly empty and the I can hear it refilling with CO2. I started by spraying all openings with starsan but I didn't see any obvious bubbling. I then reversed the keg lid and re-seated it, but still no luck. Finally, I changed all of the gaskets in both posts and the lid but it hasn't made a difference. I always use keg lube but is it possible that too much can be counterproductive? This past week I attached a spunding valve set to 10 psi and it took about 3 days to drop down to 2 psi, where it stayed until Friday. Is the beer just absorbing the CO2 out of the headspace, in the absence of all other signs of a leak?

Edit: I should say that there are no temperature changes and the beer has been properly carbonated for a few weeks. The pressure I'm applying is for serving.

 

[Beholder]

I’ve had this type of frustrating experience as well. Since it takes days, it is a slow leak, so won’t get picked by starsan. First recommendation is to get leak check spray rather than using starsan, since it is more viscous and detects slow leaks better.

I got to rip it out levels, so dropped assemblies into buckets and saw very small bubble every minute or so… in my case, it was a leak in a ball lock that didn’t seal back in addition to a poor crimp closure that would leak when the lines were touched, which explained the intermittent nature of the leak in my case.

If you have isolated it to the keg, then that’s difficult to bucket test, so the leak spray is your best bet - I’ve also had slow leaks on the PRVs that starsan simply blows out of but the leak check found.

 

[camonick]

I started by spraying all openings with starsan but I didn't see any obvious bubbling.

I have never had any luck using starsan to detect leaks. I agree with @Beholder, use a soapy spray solution or submerge the keg if you can.

 

[Docod44]

Thank you both, I'll go this route and reassess.

 

[balrog]

"disconnected" during the week means what exactly? Literally nothing connected to the keg at all, bare posts?

If so, there are only 6 places I can think of to look.
Lid big gasket, lid pressure relief gasket
Poppet gasket in and out
Oring on gas and liquid dip tubes, or, between post and keg body leak
The damnable one that got me once, the oring on the liquid dip tube, leaking gas not liquid

 

[PCABrewing]

Definitely check the poppet on the gas side. Use soapy solution, I've had those leak in the past so I have gotten into the habit of checking after disconnecting the gas for the week.
I could feel it by dipping my finger in water and putting a drop on top of the post then put finger pressure lightly on the center of the post. If it's leaking you can feel it like a slight air cushion effect.
Replaced the poppets and all was good.

 

[Beermeister32]

We’ve all had slow leaks before, very frustrating.

On the really tough ones, I’ve submerged pieces before, I’ve had fittings which defy all other methods. You could do the same with your keg.

 

[Docod44]

Thanks for all of the thoughts and suggestions. I did a full system check using soapy water starting from the CO2 tank/regulator connection and worked on down to the keg itself. There were no obvious leaks that I could find (or hear). Instead, I read in another thread that a user seats their keg lid by not clamping it down right away and instead uses 2-3 psi to push it into place before securing it. I tried this, added 10 psi to the keg and left it alone overnight with nothing hooked up to the posts. I attached a spunding valve this morning and it sat perfectly at 10 psi. I'm going to check it at various times over the following week but if it holds, I guess I haven't been seating the lid correctly.

 

[PCABrewing]

I read in another thread that a user seats their keg lid by not clamping it down right away and instead uses 2-3 psi to push it into place before securing it.

That's pretty standard practice I think.
Also I spray the lid "O" ring with starsan before putting it on the lid to allow it to squirm around a bit when seating. There's also "Keg Lube" but it is very viscous and I generally haven't found it necessary.

 

[GrowleyMonster]

Thanks for all of the thoughts and suggestions. I did a full system check using soapy water starting from the CO2 tank/regulator connection and worked on down to the keg itself. There were no obvious leaks that I could find (or hear). Instead, I read in another thread that a user seats their keg lid by not clamping it down right away and instead uses 2-3 psi to push it into place before securing it. I tried this, added 10 psi to the keg and left it alone overnight with nothing hooked up to the posts. I attached a spunding valve this morning and it sat perfectly at 10 psi. I'm going to check it at various times over the following week but if it holds, I guess I haven't been seating the lid correctly.

A very light application of keg lube on the gasket might help, too. I have one keg that will NOT hold pressure unless I do that, and even then it is not always a sure thing. I hate that keg. It is the kind with the big black plastic handle ring instead of the metal handle. Tried a new gasket, new lid, everything. The top is just slightly warped I guess. And it is a used, "reconditioned" keg. Lucky me, I got four good ones.

 

[balrog]

A very light application of keg lube on the gasket might help, too. I have one keg that will NOT hold pressure unless I do that, and even then it is not always a sure thing. I hate that keg. It is the kind with the big black plastic handle ring instead of the metal handle. Tried a new gasket, new lid, everything. The top is just slightly warped I guess. And it is a used, "reconditioned" keg. Lucky me, I got four good ones.

Try the slightly larger lid o-ring. I have a couple used kegs that require those.
This is but one example.