Beer Line Foaming - Troubleshooting Guide

We recently faced a situation with our Hard Seltzer that had been working perfectly in our kegerator system for a couple of months. In a previous post, we outlined the setup we used to adjust for the increased carbonation level of the seltzer, with significantly more carbonation and serving pressure being used compared to beer.

All of a sudden one day, the seltzer started pouring as nothing but foam. Not foaming as it left the tap and arrived in the glass, but rather coming out of the tap already as foam. Looking at the line itself coiled within the kegerator, we could see foaming, or gas escaping out of solution in there before it had even reached the tap. 

This was puzzling as nothing had changed within the kegerator at all when it started happening. We hadn't adjusted anything, or even changed a keg over, it literally started happening completely out of nowhere.

If you start researching beer (or seltzer) foaming issues from a kegerator, you'll come across the same solutions repeatedly - over carbonation and not having your system or lines "balanced" but these solutions didn't apply for our scenario since it had been working perfectly for several months with our increased line length and flow control disconnect.

We spent more time than we'd care to admit changing disconnects, lines and attaching different things to different kegs to try and isolate the problem. We eventually settled on the problem being with something related to the keg itself, and after much researching we finally found a thread on a homebrewing forum for someone who experienced a similar problem which ended up being caused by a faulty dip tube seal on the keg ball lock liquid post. Our kegs are a couple of years old now and we've never changed the seals so we figured this was a worthwhile thing to try - after all, o-rings for keg dip tubes and ball lock posts are pretty cheap and easy to come by from most homebrewing shops so we figured it was worth a shot.

Undoing the ball lock post from the keg is thankfully a really simple process - with a 17mm spanner being all that's required to undo the post. Unscrew it and remove it, but be careful not to let the spring and poppet fall out and go missing from the post once you remove it. The dip tube can now be pulled out and the o-ring is accessible.

Liquid ball lock post o-ring

Dip tube o-ring with dip tube slightly lifted

We changed the dip tube o-ring as well as the actual top o-ring where the ball lock disconnect goes and this fixed our issue. We carefully inspected the seals before doing so, and to our eye they looked fine, but there was obviously a defect in there somewhere that caused this to happen.

Our guess would be the o-ring on the post itself, rather than the dip tube as this is more susceptible to damage and wear and tear from the repeated connecting and disconnecting of ball lock disconnects. In any case, it was apparent that a leak in one of the o-rings was letting air into the beer lines which was causing the foaming to occur.

It's important to be patient when putting things back together and testing. Since we obviously had to purge the keg of all pressure prior to pulling the post off, this would have caused some foaming within the keg, so after reconnecting everything and pressurising the keg again, we waited a couple of hours for things to settle before doing some test pours which were thankfully foam free!