Non Return Valve
The function of the non-return valve is to limit the flow of fluid through it one direction. They may be manually operated or may be automatically operated. Automatic valves are designed for particular pressure, when pressure (of fluid) exceeds that limit, the valve opens allowing the fluid to flow through it. A non-return valve is fitted to ensure that a medium flows through a pipe in the right direction, where pressure conditions may otherwise cause reversed flow. Non-return valves are e.g. used with mixing loops in heating and cooling systems to ensure proper operation, and with domestic water systems to prevent backflow.