20# tank gone in 1 week, reg?

My 20#co2 tank that should last for endless kegs was finish in one week with 1/2 the beer still left.I did the bubble test from tank to tap and found no leaks.Everything is new except reg that I bought used.Its a victor 2 stage high purity reg.Is there a way of testing the reg before I buy a new one?Are they worth rebuilding?Also Ive had nothing but issues balancing setup.If the lower pressure gauge is holding steady psi but the tank is dumping is the co2 duming into keg messing up my beer? Possibly leaving my system balanced correctly and the reg is the issue

It doesn't sound like a regulator issue to me. You most likely have a leak in the system where you haven't checked. Disconnect the gas-in from the keg. Open the hand valve on the co2 tank so the line pressurizes then close the valve back up. The secondary pressure gauge should read what you set the regulator to. If the pressure drops over a period of time then you have a leak in the system somewhere between the co2 tank and the gas-in connector. It doesn't sound like you checked this part of the system before. You could have a leak at the gasket where the regulator attaches to the tank. Good luck.

No leaks at your shutoff valve for the beer line after the regulator? I lost a 10 lb tank on a cheap shut off valve that leaked.

I had the same problem when I first got my kegerator - Petro Gel and good metal hose clamps (instead of the cheap plastic ones that came with the rig) fixed me right up, I'm on Kegs #9 and 10 on one tank with plenty of Co2 remaining.