Expansion tanks are usually used in water heaters, central air conditioners and variable frequency air conditioners. This expansion tank can buffer the pressure fluctuations in the system, eliminate the water hammer can also play the role of unloading. If the water pressure inside the system has a change, the automatic expansion and contraction function, will sense the change of water pressure, and then play the role of buffer. The expansion tank can keep the water pressure stable and control the pump from changing due to the pressure. At the same time, it will not be turned on and off frequently.