Last week before our big trip I switched out tanks to a fully filled one. When we got to our site and set up, I opened the valve and heard and smelled gas. I disconnected and reconnected with no luck so we left it disconnected and valve off. When we got home, I switched out tanks with the BBQ one, no leak. Put original leaky tank on BBQ and it leaked there also. So I know the issue is with the tank and not the pup connection. The O-ring in the valve looks "smooshed" compared to the non leaking tank so I am thinking the O-ring is the culprit. Is this O-ring replaceable? Do I need a special tool or technique to get the old off and new on? and finally, is this a hardware store item or a specialty item from a propane dealer? Thanks in advance!