What is an expansion tank?

An expansion tank is a device that stores hot water and is widely used in homes, businesses, and industries. Combined with the hot water heating system, it can help adjust the water pressure of the system, prevent the bursting of the system’s water reservoir and pipes, and achieve a more stable, safe and efficient heating effect. I believe many people must have the same doubts as me, why is the appearance of a rectangular water tank designed to have an expanded shape? There must be a certain reason why the water tank is designed like this. Today, the editor of Aike Water Tank will let you know what an expansion water tank is and its function. 

Expansion tank

hdp water tank

The expansion water tank is a container made of welded steel plates, usually round or rectangular, and available in various sizes. It is an important component in the hot water heating system and central air conditioning water system. Its function is to contain and compensate for the expansion and contraction of water in the system. Generally, the expansion water tank is set at the highest point of the system, and is usually connected to the return main pipe near the water suction port of the circulating water pump (central air-conditioning chilled water circulating water pump). The expansion water tank is usually connected to the following pipes, including: expansion pipe, overflow pipe, signal pipe, circulation pipe, drainage pipe, and water replenishment valve.

1.Expansion tubeIt transfers the increased volume of water in the system due to heating expansion into the expansion tank (connected to the return water trunk).

2. Overflow pipe:Used to drain excess water above the specified water level in the water tank. When the water expands and the volume of water in the system exceeds the overflow pipe opening, the water will automatically overflow and can generally be connected to a nearby sewer.

3.Signal tube:Used to monitor the water level in the water tank. It can be connected to the sewage basin of the bathroom or toilet on the ground floor of the building, or it can be connected to the boiler room. Generally, it should be connected to a place where people can easily observe to see whether there is water in the expansion tank.

4. Circulation pipe:When the water tank and expansion pipe may freeze, it is used to circulate water (at the center of the bottom of the water tank, connected to the return water trunk). Connect it to the horizontal return main pipe in front of the system’s constant pressure point. A distance of 1.5~3m should be maintained between this point and the constant pressure point, so that part of the hot water can slowly flow through the water tank through the expansion pipe and circulation pipe to prevent the water in the tank freezing.

5. Drainage pipe:It is used for cleaning and emptying the water tank, and can be connected to the nearby sewer together with the overflow pipe.

6. Water replenishment valveIt is connected to the float ball in the box. If the water level is lower than the set value, water will be replenished through the valve.

What is an expansion tank?

Water tank volume calculation


In the formula V一The effective volume of the expansion tank (that is, the volume equivalent to the height between the inspection pipe and the overflow pipe),L;

a- expansion coefficient of water per unit volume,a=0.0006;

Δt一Consider that sufficient water capacity should always be stored in the expansion water tank to compensate for the shrinkage of the volume of the water in the system when it is cooled. The maximum fluctuation value of the water temperature in the system is generally calculated based on the water temperature of 20°C;

Va- Water capacity in the system,L。

Regular maintenance and upkeep

Expansion tanks, although they play a critical role in the system, generally require less maintenance. However, regular inspection and maintenance are still necessary to ensure proper operation. Here are some maintenance suggestions:

1、Check the pressure: Check the pressure in the expansion tank regularly to make sure it is within the normal range.

2、Check the seal: Make sure the expansion tank seal is intact to prevent leaks.

3、Cleaning: Keep the outside surface of the expansion tank clean and check the inside regularly for accumulated sediment.

Heating or air-conditioning systems should generally be equipped with high-level expansion water tanks where permitted. If conditions are limited, a set-pressure tank or variable-frequency water pump can be installed for constant-pressure water replenishment. The expansion water tank is used in a closed water circulation system to balance the water volume and pressure to avoid frequent opening of the safety valve and frequent replenishment of the automatic water replenishment valve. In addition to containing the expansion water, the expansion tank can also function as a water replenishment tank. In short, the expansion tank plays an indispensable role in the hot water heating system and hot water supply system. It helps to maintain the system’s Operate properly and ensure stable pressure. Understanding the role and importance of an expansion tank can help you better understand how your system operates and can help ensure the long-term health and reliability of your system.