Block water backflow and convey water flow one-way through pipe with the PVC Air Check Valve, 1-1/2 in. IPS S X 2 in. Spigot. Water is allowed through the valve when the water pressure is greater than the weight of the 1/4 lb spring. This leak-resistant valve connects 1-1/2 in. pipe to 2 in. pipe in an irrigation or other pressurized system and prevents the backflow of water. Prevents costly property damage, pipe corrosion, and system issues. Durable check valve is made of clear PVC plastic. Pressurized Spring is made of stainless steel. Washer is made of silicone. Use fittings and other valves to set up a new irrigation system, expand an existing system, or make repairs.