Pressure tank uses air compressibility to regulate and store water and makes water maintain the required pressure, so it’s also called water pressure tank. Its role is equivalent to the water tower or high located pool. Since its water-supplying pressure is maintained by compressed air in the tank, the installation height of the tank can be unlimited. It is suitable for small and medium-sized villages where water is adequate and electricity supply is stable because of the less investment, fast construction speed, easy demolition, high flexibility, and high degree of automation. However, it’s not suitable for users needing large quantities of water and constant pressure because of its small amount of water regulation, fast pressure reduction, frequent start-up of the pump and high operating costs.
Pressure tank is generally installed between the distribution pump and pipe network. After the pump is started, the water is supplied to the pipe network and excess water is stored in the tank. The water level in the tank rises and the air in the tank is compressed, which causes pressure increase accordingly. When the pressure in the tank reaches the specified upper limit, the indicator of the pressure gauge which installed in an electric contact connecting pipes and the top of tank will reach its upper limit and then, a signal is sent to cut off the power and stop the pump. When users continue to use water, water inside the tank will be pressed into pipe network by compressed air in the tank. When the water level goes down, air pressure also falls in the tank. When air pressure falls to the required lower limit, the indicator of the pressure gauge installed in the electrical contact will reach the lower limit, and the relay works. Then, the machine is electrified and the pump restarts the work. Under normal circumstances, the pump can work under unmanned control, and according to changes of water consumption, adjust opening and stopping times and working hours to ensure continuous water supply to the pipe network.
Pressure tank has two types, air-filled and diaphragm. Air in the air-filled pressure tank has direct contact with water. After a period of time, the air reduces due to leakage and dissolution in water, so its amount of water regulation gradually reduces. Then, starting pumps gets more frequent. So, regular air-replenishing is needed. Ways to replenish air include air compressors, air-jets and regular water-draining to fill air. Diaphragm-type pressure tank separates gas from water. Water is inside the rubber (plastic) capsule. The gap between the external and the tank body pre-filled inert gas, which is nitrogen generally. This pressure tank doesn’t have the problem of air loss into water. One time of air inflation can be used for a long time, so the air compressor is unnecessary. As a result, investment is saved, the system simplified and the scope of use expanded.