With 300 psi working pressure packed into this 4-inch valve, the CV-300B can create one-way water direction for your fire safety system. As a swing check valve, it creates water flow in one direction and prevents back flow. These valves can even be used vertically to make water flow upward. An arrow is cast into the valve for intuitive installation. Point the arrow in the direction you want water to flow. An elastomer seal is designed to reduce leak risk.