i spent 45 minutes with a very nice 40 year veteran in our industry who walked me through how the Griswold is able to avoid the last 20% closing problem. So I am satisfied beyond any doubt that the Griswold belongs in its own category. No other valve is built like it which is about 99% of those in use is my guess. For them the 20% closing problem still exists as well as opening surge pressure from poor valve location and installation. He also said MVs don't eliminate surge pressures which is why the top designers use N.O. no surge anticipation valves connected to a flow sensor. (model 2265) So if you have water hammers and don't want to correct the real problems causing them then just toss in a Griswold MV with a new controller that has a zone delay feature. (I'm aware of zone delay controllers. I mentioned unless you have a controller that allows for a delay.) As for Leary opening the MV before turning on any zones doesn't seem too wise to me. You want a zone open with the MV opening or use a NO and leave the mainline charged at all times. NOTE THE SECOND SPRING. (29) That combined with the metering pin is the key.