By Patrick Gordon of Calafrica (

Q – What is a deaerator device?

Patrick Gordon

A: We have all come across an aerator that is fitted to a terminal fitting. These are used to add air to the water and the result is to break up a laminar flow. The deaerator does the exact opposite, it removes all the air from the plumbing system. Let us have a look at the need for, and the use of, a deaerator device. Deaerators are used to continuously remove the air contained in the hydraulic circuits of heating and cooling systems. The air discharge capacity of these devices is very high. They are capable of automatically removing all of the air present in the system, down to micro-bubble level. The circulation of fully deaerated water enables the systems to operate under optimal conditions, free from any noise, corrosion, localised overheating or mechanical damage.

Micro-bubbles develop where the speed of the medium is particularly high, with a corresponding reduction in pressure. These points are usually the pump impellers and the water orifices of the regulating valves. These microbubbles of air and steam, the formation of which is accentuated in non-deaerated water, may subsequently implode because of the cavitation effect.

So how does a deaerator perform this magic? The deaerator utilises the combined action of several physics’ principles. The active part consists of a set of concentric metal mesh surfaces (1). These elements create the swirling motion required to facilitate the release of micro-bubbles and their adhesion to the surfaces.


The bubbles, fusing with each other, increase in volume until the hydrostatic thrust is sufficient to overcome the force of adhesion to the structure. They then rise towards the top of the device and are expelled through a float-operated automatic air vent valve (2) see article in the June 2023 edition of Plumbing Africa]. It is designed in such a way that the direction in which the medium is flowing inside the deaerator makes no difference.


The deaerators can also be supplied with an insulating shell to make thermal lagging easier. Deaerator devices may be used in both heating and cooling circuits, to guarantee progressive elimination of the air which forms continuously. They should preferably be installed vertically after the boiler, on the pump suction side, as this is where the formation of micro-bubbles is most prolific.


All things considered; the deaerator is a handy device that can increase the longevity of your hydronic system.

For any further information regarding this topic please feel free to contact:

Patrick Gordon at +27 (0) 83 303 1437

Images supplied by Patrick Gordon