Washer between co2 tank and regulator

I emptied 5 LBS co2 tank in 1 week, I think I have a leak, my question is I reused the washer between the CO2 tank and the regulator, could this be the site of the leak, basically are these washers one time only deal, how do you know when they are no longer good if they are multiple use

You must have drank a lot! I have reused those washers with no problem. If I remember right they have a raised ring on one side that seats either to the regulator surface or tank valve body. I have a permanent seal that screws into the end of the tank valve. And has a rubber o ring in it. You could try putting a little keg lube at the connection next time.

Check all your connections with soapy water you may learn the leak is not at the regulator. It could even be a leaky connection on your kegs or a prv. Some of the cheaper check valves can develop a leak too. There are so many places, so be diligent in your investigation.

I have changed all my o rings when I got the kegs first time using these kegs, would it leak if I put washer in backwards

I’ve read they’re one time use, but I got a new one with a 5# tank that I reused with my 10# tank.