Quote Originally Posted by Herzeleid View Post
No not the fill & drain cap, I refer to the big one that closes the tank.
Yup. It can be a real pain. Rub the inside of the lid and the place where the lids goes with very fine steel wool. Then scrub both thoroughly and dry. Next put a very, very thin layer of lubricant like WD-40 on the tank part. Rub it on with your finger. That should do it. If it does not, one old trick is to take a thick rubber band and put it around the gripping area of the lid.

I solved that problem, and one other, in this manner: I cut some of the adhesive appliques used to make non-stick shower and step surface surfaces--some dark, some light-- and placed a piece the same color on both the lid and the tank. They provide a non-skid gripping surface, and also ID which lid goes to which tank.