Perhaps one of the more frustrating items when homebrewing can be running out of gas in your co2 tank. Even more frustrating is when a brand new tank lasts but 5 or 6 days. This happened to me in the last week. Co2 refills are not dirt cheap, they cost about $21 for a 5 pound tank. The hardest part is usually finding the leak. I've had my kegerator for years and the same gas distribution for the last 6 years. I am hoping in this instance the regulator was just not on quite tight enough. I checked all of the gas fittings and the keg that is on tap with star San which should bubble if there is a leak and I haven't found anything so far. I will need to do a thorough checkup this weekend to see if I can't nail down this leak.