The Trap Priming Distribution Systems are patented designs that incorporate both copper and PVC materials. These designs give the installer a simple and positive means to prime multiple floor drains using only one Precision Plumbing Trap Priming Valve. It is our recommendation that the distribution unit be mounted level. The fresh water supply line, running from the distribution unit to the trap, must be a minimum of 1/2 in O.D. copper tube.