My Grey water tank #1 (Galley tank) is not closing all the way. I've taken the plate off in the docking center and looked at the handle end and also opened the belly and looked at the valve end. They look OK, in fact I had the better half open and close it while I looked at the valve. Looks OK so I'm thinking that there is an adjustment on how far the valve gets pushed in. Does anybody know if there is and how do you adjust it?