How a expansion vessel works

The principle of operation of an expansion vessel is based on the accumulation of hydraulic energy of water and its subsequent use. Below is the principle of operation of an expansion vessel using the most common connection scheme with a booster or well pump.

An elastic membrane hermetically divides the tank volume into two chambers - gas and water. The membrane can stretch in such a way that the entire volume of the expansion vessel will be filled with gas or water. The gas chamber is connected to the atmosphere through a nipple and initial pressure can be created in it with the help of a compressor. The water chamber is connected to the water supply pipeline through a flange.

The filling of the expansion vessel with water begins upon signal from the pressure sensor, which sends a signal to turn on the pump when the value of Pmin is reached. The operation of the pump leads to an increase in pressure in the water supply system up to the maximum allowable level of Pmax and the entry of a reserve volume of water into the expansion vessel, while the gas is compressed and its share of the volume in the tank decreases. The pump is set to turn on at the pressure of Pmin and turn off at the pressure of Pmax.

A slight water flow, such as opening one faucet, does not cause the pump to turn on and is covered by water displaced by compressed gas from the expansion vessel. After all the water reserve is displaced from the expansion vessel and the minimum pressure is reached, the pump will turn on.

The calculations section of the website provides a program that will help you determine the initial pressure of the gas space Pg, the pump turn-on pressure Pmin, and the pump turn-off pressure Pmax under specific conditions.

Attention! The expansion vessel is intended for clean drinking water. It is prohibited to use it for flammable, chemically active liquids, as well as water containing abrasive substances and other solid objects that lead to intense wear of the membrane.

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