No negative pressure variable frequency water supply equipment put into use, water into the water pipe network flow tank, the tank air from the vacuum eliminator discharge, wait for water filled, vacuum eliminator automatically closed. When the pressure of the water supply network can meet the water demand, the system supplies water directly from the bypass check valve to the water supply network, and when the pressure of the water supply network can not meet the water demand, the pressure signal of the system is fed back to the frequency controller by the remote pressure gauge, and the water pump is operated, then start another pump frequency conversion operation. When the water supply pump, if the water supply pipe network is larger than the pump flow, the system to maintain normal water supply: water peak, if the water supply pipe network is smaller than the small pump flow, at this time, the air from the vacuum eliminator into the tank, tank vacuum was destroyed, to ensure that the water supply network does not produce negative pressure, after the peak of water consumption, the system is back to normal water supply. When the water supply network shut down, the liquid level of the steady-flow tank drops continuously. The liquid level detector feedback the signal to the inverter controller, and the pump stops automatically to protect the pump unit. At night when the water supply is small and the pressure of the water supply network can not meet the requirements, the air pressure tank can store and release energy, thus avoiding the frequent start-up of the water pump.