Zoeller 2" slip x 2" slip cast iron union check valve that features full 2" flow design, 2" full flow pump code, and a neoprene gasket and flapper, weighted with heavy stainless steel metal backing plates and stainless steel rivet. This valve checks backflow of water and sewer gas. The flexible neoprene slip x slip union includes stainless steel clamps for low pressure systems. Avoid more than 10' static head above the check valve. 4.3 psi at 130°F. Model 30-0151 has a corrosion-resistant, powder coated epoxy finish.