Iv been having an issue and im probably doing something entirely wrong here. But. Iv been having some some residential systems with newly REPLACED (cut out and replumbed) Master Valves allow water to leak past/thru the MV and then leak 24/7 out of either a mainline compromise or another slowing leaking-thru valve. I suppose I have for a very long time been in a complete misunderstanding of the purpose and reason for a MV (on small resi systems). Its goes without saying with me of course that the other compromises down the line need to be addressed each and every time as well , HOWEVER, my question and focus remains for this question on the MV. Why arent these new 1" slip PGVs (my current go to valve) not closing when in a Master valve arrangement? Are the zone valves closing too soon? : not allowing the Master valve the minimum flow rate required to fully close the diaphragm?