Both the backflow preventer and the check valve function to prevent backflow, but the two are different and have essential differences. The backflow preventer consists of two spaced check valves and a drain valve. Due to the local head loss of the check valve, the pressure in the intermediate chamber is always lower than the pressure at the water inlet. This pressure differential drives the drain valve to a closed state and the line is properly supplied with water. When the pressure is abnormal, (ie, the pressure at the outlet end is higher than the intermediate chamber), even if the two check valves cannot be reversely sealed, the safety drain valve can automatically open to vent the backflow water and form an air partition to ensure the upstream water supply. Health and safety.

1. Backflow preventer According to China's current water supply pipe network, especially when the drinking water pipeline has serious backflow pollution, and there is no effective prevention of backflow pollution device, a kind of strict restriction on the water in the pipeline can only be one-way flow. New hydraulic control unit (backflow preventer).

2. The backflow preventer product consists of two separate check valves and a hydraulically driven drain valve. Due to the local head loss of the check valve, the pressure in the intermediate chamber is always lower than the pressure at the water inlet. This pressure differential drives the drain valve to a closed state and the line is properly supplied with water. When the pressure is abnormal, (ie, the pressure at the outlet end is higher than the intermediate chamber), even if the two check valves cannot be reversely sealed, the safety drain valve can automatically open to vent the backflow water and form an air partition to ensure the upstream water supply. Health and safety. It is a hydraulic control combination device that strictly limits the pressure water in the pipeline to flow only in one direction.

3. Check valve: Check valve is also called check valve or check valve. Its function is to prevent the medium in the pipeline from flowing back. The valve of the opening and closing member is opened or closed by the flow of the medium and the force to prevent the back flow of the medium from being called a check valve.

4. The check valve belongs to the automatic valve type, which is mainly used on the pipeline with one-way flow of the medium, and only allows the medium to flow in one direction to prevent accidents. The check valve is divided into structures according to the structure, and can be divided into three types: lift check valve, swing check valve and butterfly check valve. The lift check valve can be divided into vertical and horizontal swing check valves, which are divided into single-valve, double-valve and multi-lobed. The butterfly check valve is straight-through type, and the above several check valves can be divided into three types: thread connection, flange connection and welding. The check valve is a valve that automatically prevents the fluid from flowing backwards. The valve flap of the check valve is opened by fluid pressure, and the fluid flows from the inlet side to the outlet side. When the inlet side pressure is lower than the outlet side, the valve flap is automatically closed under the influence of fluid pressure difference and its own gravity to prevent fluid backflow.