Why should you remove air from your system water?

In a heating or cooling system, heat is transported from the heating or cooling unit via the system fluid (mostly water). Stacked air in the system will harm the performance and efficiency of your system as it disturbs the free flow of the system water.

Many of you will already know that when you (re)fill and pressurize a heating system with tap water, you need to ensure that air is removed from the system. You may have to repeat this process several times to ensure the system is filled and pressurized. However, the pressure of the system can fluctuate based on the temperature of the system water, thus, air reentering the system through connections, valves, etc.. In part, depending on the pressure and temperature in the system, the air is already present in water.

Air in the system is frequently responsible for costly and high-maintenance failures
Symptoms of air in your heating system

Problems caused by air in your heating system

Air causes loud noises in radiators, heat exchangers, pipes and pumps. It makes it extremely difficult to adjust systems and it promotes corrosion, and thus, the formation of dirt and magnetite. Air in the system leads to a significant reduction in heating and cooling performance, and premature wear and tear on major system components, or, much worse, a blockage.

This, in turn, could lead to a complete failure of the system and all the hassle that comes with it, such as dissatisfied consumers and residents. If a system is designed and operates without an air removal solution, it becomes much easier to predict how the system will perform in the medium to long term future.

The 3 appearances of air in system water

As already mentioned, system water will always contain air, which can be present in 3 different ‘appearances’:

Free Air

Free Air

This is the air that is locked in the system, also known as airlocks. These airlocks prevent effective transport of heat or cold in your system.


These are small, air-filled bubbles which are (sometimes) hardly visible in the water
Dissolved Gases

Dissolved gasses

Water always contains, non-visible, dissolved gases such as nitrogen, oxygen, and carbon dioxide

Removal of dissolved gases using a vacuum degasser

The SpiroVent Superior uses a vacuum to degas the system water. They can be equipped with an automatic degassed (re)fill function and can also monitor the system pressure, keeping it at a constant level.

In a vacuum degasser, a small amount of the system water is depressurized. This means that dissolved gasses are extracted from the system water (into free air) and can be removed from the system. The degassed water is released back into the system where it can absorb free gasses again. This is a continuous process that results in a system that almost holds no dissolved gasses anymore.

Our solutions for effective air removal

The positioning of an air vent, air deaerator or a vacuum degasser in your system

Air vents are best positioned at the highest point in the installation to prevent air pockets. Air deaerators are preferably positioned at the hottest point of the installation, the point where the water leaves the heater or where the water enters the cooler.

Since a Superior uses depressurization for dissolved gasses removal, the position isn’t that crucial.  A vacuum degasser should be used for systems:

  • with many branches and a low flow velocity or
  • systems with a small temperature differential, or
  • where an inline air deaerator cannot be installed, or
  • where it cannot be predicted where gases are released from the water or
  • when that point has a very low flow rate.