[HayZee518]

The vacuum relief or back siphon valve is a requirement in certain cities and jurisdictions to prevent brackish water from entering the system by a back siphon action. That's like if you had a hose in a laundry tub full of soap suds and for some reason you lost your positive pressure in the system - you'd create a suction that would back feed the soap suds into the system main. Probably wouldn't hurt anybody but its just a safety precaution. As far as the extra valves, probably you wouldn't need them, but personally I put in valves all over the place, at least I can isolate or bypass areas of my own house without jeopardizing the rest of the house.