The way my system is is I have a 7.2 cubic ft keezer that I keep three kegs, a 10lb CO2 tank and a three-way manifold. I only have the one regulator (actually I do have an addition, but I havent gotten around to attaching it yet), so for the longest time I have been carbing and serving at the same pressure. I just set the keg on 13psi and let it sit for a while. The pressure is a little on the high side for serving, but with 6ft of line and holding it over my head, 99 times out of 100 it is a perfect pour. However, over the weekend, I poured a Kolsch and it was all kinds of foamy and I noticed it seemed to be pouring faster. I checked the reg and my pressure said that it was 18psi. So I turned the screw maybe a quarter turn counter clockwise and off gassed the kegs. Then last night I went to pour a steam beer and it was even worse. I checked the reg and it was up to 22 psi!! So I gave the reg about a half turn counter clockwise, off gassed, and I have yet to check it today. I am sure that I will be able to get it dialed in again, so I am not worried about that, but what could cause the pressure to just change like that? I keep the tank in the fridge with the kegs, temp is set at 42. The tank was last filled, oh I dunno, two months ago.