Fire-fighting gas top-pressure equipment uses capsules as gas-water isolation, once inflated, and used throughout the year. When working, start the pressure-stabilizing pump, the water chamber enters the water, the water pressure rises, and the gas in the air chamber is compressed. When the water level drops, the gas in the air chamber expands, and the diaphragm contracts, compressing the water in the water chamber. The electric pump is controlled by the electric contact pressure gauge and the electric control box to reach the rated pressure. The total volume of such a pneumatic tank is relatively large. For example, when the effective volume is 3m ^ 3, the total volume is 6.3m ^ 3; when the effective volume is 6m ^ 3, the total volume reaches 18m ^ 3. Due to the manufacturing process, the maximum effective volume of such a diaphragm tank is generally 6 to 7 m ^ 3, which can only meet the needs of buildings with an indoor fire hydrant water consumption of 10L / s, and cannot meet the high fire water demand.