The Taco 003, 005 & 006 Plumb n' Plug® (PNP) periodically re-circulates hot waterthrough the domestic piping system to decrease the delivery time to outlet fixturesand reduce wasted water. Typical timer programming will cycle the Plumb n' Plug during high peak usage periods such as early morning or early evening. An optional aquastat is available for constant circulation applications to maintain temperature between 95˚F and 115˚F. The Taco 003 PNP is ideal for recirculation loops.Its design operating condition of 3 gpm at 3 ft of head helps to reduce erosion corrosion and noise in system piping. Use the 003 PNP for systems up to 200 total ft (supply and return) of 3/4 in pipe. The Taco 005 & 006 PNP's are designed for systems using 200-400 ft of 3/4 in pipe. Installation of isolation valves, pipe insulation and flow checks are recommended.