Fire Sprinklers - Double Check Valve
A Double Check Valve (otherwise known as a Backflow Preventer) is used to stop stale water from a fire sprinkler system flowing back into the potable water system.
I need one with a diameter of 1.25" (or greater, up to 2"). If there is not much price difference then getting a 2" one is best.
http://www.pexuniverse.com/wilkins-950xlt2 1.5" $258.95 + $0
My existing 1" one is from Ames, but here is the 2" version...
List of suitable approved products...