Box no negative pressure device by piping, pumps, tanks, pressure pump and control system, two routes into the water tank, all the way into the device steady flow tank, pipes are fitted with electric valve and transmitter, After the equipment is installed, according to the user's need to set to meet the most unfavorable point of constant pressure water supply, when the water pressure to meet the constant pressure, direct supply by straight lines. This device is suitable for hotels, guest houses, schools, hospitals, pipe end and a small pressure regions.