I've been losing CO2 rather quickly since I started kegging my homebrew this past summer. Prior to that, I used my kegerator for several years using only commercial kegs. My 5lb CO2 tank lasted more than 2 pony kegs on a single fill during that time. Since then, I've not been able to force carb and drink a full, 5 gallon keg without having to get my tank refilled. I tried to diagnose the problem on my own and several times I had the problem figured out. The way I've usually found the following problems is by spraying star san on these areas and watching for bubbles. Normally, I've been able to detect the faint hiss of leaking air as well. There was first a leaking seal on the lid - a little keg lube did the trick. Then a leaking relief valve on the keg - again keg lube did it but I also now have a backup relief valve on deck Leaking 500 series Perlick faucets - upgraded one to the 600 series and the other has gone back to my original standard faucet for now. Hose Barbs on air hoses - Never detected a leak but was using 1/4" hose barbs in the 5/16" air lines at the connection to the air tap. These are now upgraded to 5/16" Most recently (mid-February?) I tried to start at my tank and put on component by component looking for a leak. I upended my tank in a bucket of water and looked for bubbles - none. Then I attached the regulator with the pressure turned all the way down and sprayed star san on the connection to the tank and the body of the regulator (specifically the relieve valve on the back) - no bubbles. Next one air line with starsan on all the connections and fitting, then the other - nothing. Next I attach to both my kegs and check all over them for leaks - none. Finally the beer connections... you see where this is going. I did give all the hose clamps an extra 1/4 turn and that sort of thing and hoped this would do something. My system is a 5 lb tank with a standard beverage factory regulator and a y splitter. Currently one side goes to a 5 gal keg and the other to a 2.5 gallon keg. I filled my tank on 2-23-16 and at the time my 5 gallon tank was already carbed so gas has just been used for serving since (maybe 5 pints). I did force carb the 2.5 gallon tank and have only served one pint out of it so far. There was just a little bit of loss in testing component by component as well but still, very little. I can tell by my gauge, I'll be out in just several days so let's say 3-15-16 - it will last just 3 weeks. I'm almost at the point of giving up on kegging completely. This has been a long and expensive experience in trying to diagnose the problem and getting the tank filled about 8 times now since this past summer when it went on one fill for over 2 years prior to that. The only thing I can think at the point is the regulator as I was hesitant to really coat it in star san as I didn't want to mess it up by getting the interior wet. Any help would get greatly appreciated!