When water enters the water tank from the public pipeline network, a portion of it directly enters the tank. When the water level reaches its maximum limit, the inlet float valve of the tank closes; The water level drops and the inlet float valve opens. The other part enters the non negative pressure regulator. When the pressure in the public pipeline network is sufficient and the water supply unit is running, the non negative pressure regulator starts to operate, using the existing pressure in the pipeline network to directly supply water to users. When the pressure in the public pipeline network is insufficient, the negative pressure monitoring meter immediately feeds back the signal to the negative pressure control center as soon as it detects the formation of negative pressure in the pipeline network. The negative pressure control center receives the signal and immediately sends a command to the non negative pressure regulator. After receiving the command, the non negative pressure regulator starts to automatically adjust the pressure to prevent public pressure from entering. At the same time, the water supply channel of the water tank is opened, and water is directly supplied from the water tank to the user's pipeline network.