Intermittent Foam - Dip tube leak?

[mashdar]

I have a keg of hefeweizen exhibiting intermittent foam on every pour. At 20psi I thought it was the pressure, but now even at 12 it's happening.

Duty cycle is ~1/4 with period ~2s.

I'm using a picnic tap 2.0, and tried swapping it in case there was a gasket out of place, but no dice.

I'm wondering if the dip tube gasket could intermittently gulp some headspace CO2.

Any thoughts?

 

[IslandLizard]

I'm wondering if the dip tube gasket could intermittently gulp some headspace CO2.

The gasket on the liquid diptube, right? It could be, a small leak there can allow headspace gas to enter the beer line. If that's the case, you'll see a train of bubbles in the beer line.

 

[mashdar]

The gasket on the liquid diptube, right? It could be, a small leak there can allow headspace gas to enter the beer line. If that's the case, you'll see a train of bubbles in the beer line.

You wouldn't expect on/off foam behaviour?

It's particularly odd, as there's no gas connected, so whatever it is is a property of the diptube-coupling-qd-dispenser system.

I've had some issues with QD pin mating; maybe it's a marginally open QD or something.

 

[day_trippr]

Might be worth pulling the long dip tube and while you're there make sure there's nothing plugging the Out post or beer QD...

Cheers!

 

[mashdar]

Might be worth pulling the long dip tube and while you're there make sure there's nothing plugging the Out post or beer QD...

Cheers!

I'll probably just live with it rather than let some air in; it's plenty drinkable, if a bit unsightly.

Once it's kicked it'll get a thorough inspection and mark it for low-priority next use.

The short periodic nature feels like it should be textbook X, but I'm not sure what X might be.

edit: Thinking back on it, I may have seen this keg do this on past batches to a lesser degree.

 

[IslandLizard]

I'll probably just live with it rather than let some air in; it's plenty drinkable, if a bit unsightly.

If it gets too annoying, you could easily check or replace the (liquid) keg post with a known working one after depressurizing the keg. While the post is off take a gander at the diptube o-ring, or replace it. Only takes a minute, or two, max.

When done, as usual, purge the headspace a few times and re-pressurize.

 

[Bobby_M]

The non-invasive way to check is to carefully tip the keg over in the direction that puts the liquid post at the lowest spot on the diameter of the keg. Just tip it enough so you can be sure that area of the liquid post underside is flooded with beer. If the bubbles go away, you're getting CO into the liquid path. I'm aware of one pinhole leak in the weld of the diptube itself. The keg would pour great until there was less than 3 gallons then foam foam foam. That was the pinhole getting exposed to CO2 headspace. The other time I had it was the spring of the universal poppet was threading itself around the top flange of the diptube and putting a space between the flange and the oring underneath.

 

[mashdar]

The non-invasive way to check is to carefully tip the keg over in the direction that puts the liquid post at the lowest spot on the diameter of the keg. Just tip it enough so you can be sure that area of the liquid post underside is flooded with beer. If the bubbles go away, you're getting CO into the liquid path. I'm aware of one pinhole leak in the weld of the diptube itself. The keg would pour great until there was less than 3 gallons then foam foam foam. That was the pinhole getting exposed to CO2 headspace. The other time I had it was the spring of the universal poppet was threading itself around the top flange of the diptube and putting a space between the flange and the oring underneath.

That's such a good idea that you've driven me to day drinking. (Good thing it's 3.2% and only took a few ounces!)

Tipping it over eliminated the foaming issue. I'll inspect the seams when it's empty, as that's not something I would have thought to check. Thanks!