A butterfly valve controls the flow of liquid through pipes with a rotating disc mechanism that flaps like a butterfly’s wing. A handle on the valve is turned to open and close the disc to permit, prevent and control the flow. A large piping system, like the one found in your home, often contains multiple butterfly valves. Each valve is linked by segments of pipe and controls a specific quadrant of the system. A butterfly valve connects to the existing pipe in your home. Once you've connected them, assemble each butterfly linked to the piping system.