If you saw my last post, you see I am stripping all the contents of the JC sprinter to replace damaged and wet sub plywood. I have removed most internals, just the grey water tank out. I have removed the 3 fixing bolts but it's connected via the underside drain point. I am assuming the drain connector is attached to the bottom of the tank by the round upper ring? I have tried turning this with a couple of wrenches but it is stuck tight.Any comments appreciated.