I've been kegging for about 6 weeks now, after picking up a great Craigslist deal on a system from someone who knew nothing about brewing or kegging. The regulator I got has what appears to be a homemade 2-keg manifold assembled from pipe fittings. I noticed pretty quickly that there are no check valves in this setup but it has worked fine so far with one keg at a time.
On Saturday I took a keg to a party, first time I've traveled with the system. Everything went well and the beer was much appreciated and disappeared quickly. When I got home late Saturday I was a bit intoxicated and exhausted from running around all day, but knew I needed to reconnect the CO2 with another keg that has been carbing for a few days. My regulator was still at serving pressure from the party but the keg was much higher from carbonating and when I plugged the two together I heard a hissing sound that didn't sound right. Immediately remembering the difference in pressures and lack of check valves I thought I might have gas/beer flowing back out of the keg and into my regulator so I quickly cranked the pressure up to push everything the other way. The hissing stopped, everything seemed stable, so I closed the freezer and went to bed.
First thing Sunday morning I checked the system to make sure nothing was leaking and, sure enough, the high pressure gauge was at zero. On closer inspection I realized the needle was below the pin, not resting on it... My tank still has CO2 and the needle will jump a bit when I turn the tank valve off and on, but I am quite confused as to how the needle got to the other side of the pin. Could this happen due to beer backflow into the regulator? Or maybe from banging around in the back of the car on the way home from the party? Are beer gremlins now plotting against my glorious keg beer? Did I somehw manage to create several thousand PSI of pressure and spin the needle all the way around? Most importantly, how do I keep this from happening with the next gauge I buy?
