[Mal Bridgeman]

I don't know how the internals of an MDE valve work, but on my valves I have to remove the "slug" to clean it and grease it for smooth operation. .... which can only be done on an empty set.

HTH
Mal

P.S. Don't let NickB or Gary (WWD) know that the MDE valves need maintenance - that really would be the final straw