Evaporative air cooling systems draw air over wet pads and surfaces. This results in the evaporation of water into the air which reduces the air temperature and increases its moisture content. The cooled humidified air cools the inside area before exiting via the open windows, doors or mechanical ventilation openings.

Cool air can only get into the home if the hot internal air has a way to get out. Airflow rates are generally high and these systems are most effective in hot, dry, low humidity climates and where increased indoor humidity levels do not adversely affect comfort.

Evaporative air coolers use electricity to generate and distribute the cooled air via their fans and pumps. Water is consumed by evaporation to produce the cooling effect and by the unit water quality management system, which is designed to minimise salt build-up within the water reservoir. That is why it is important to know if the water quality have an effect to evaporative cooling performance.


Rainwater can be used to substitute or supplement the water supply to an evaporative air cooler as long as it is clean (drinking water quality) and secure (not open to contamination).

Recycled Water

The quality of recycled water can vary significantly and using this water source as a supply for your evaporative air cooler is not recommended without seeking expert advice.

Drain Water

The water that is drained from the evaporative air cooler may have elevated salt levels. This water may be suitable for reuse as irrigation water (of salt tolerant plants) or for non-critical water uses such as toilet flushing or even washing clothes. This water should never be reintroduced into the drinking water supply or used as drinking water.

Water Storage and Reuse

Because evaporative air coolers tend to wash the air of dirt and dust, the drain water can contain nutrients and microbes as well as elevated salt levels. Similar to grey water, the storage of this water can encounter microbial growth problems and instantaneous use (without storage) is recommended in residential applications, unless the water is treated.

Drain Water Salinity

Salinity is most easily measured using an electrical conductivity (EC) meter, the higher the salt concentration the more electrically conductive the water will be. Special hand held salinity meters are available for this purpose.

Water Waste

Studies have shown that many evaporative air coolers have been installed with the default factory settings unchanged. In many systems this involves the unit “dumping” or “bleeding” significant quantities of water to the drain for the full length of time that the system is turned on. This water consumption is often either excessive or not necessary and represents a significant waste of water and an increase in operating costs.