Improve the water efficiency of your evaporative air con

When summer rolls in, the first thing we do to beat the heat is reach for the air con remote. While evaporative air conditioners are energy efficient, they can use a lot of water. Especially when left on the default settings.

It could be a reason for a high water bill this summer.

Evaporative air conditioners filter warm air through water-soaked pads. The resulting evaporation cools the air. Steady water flow is the crucial element of the evaporation cooling process. Water is also used in the unit's quality management system to minimise salt build-up.

Around 100 litres of water an hour can be evaporated from the pads in Perth’s hot weather. This adds up to 30,000L* or more to your yearly water use (calculated based on 6hrs/day for 50 days). In drier areas, this can be a lot higher.

Save water when cooling your home

Here are some simple ways to maximise the water efficiency of your evaporative air conditioning system.

• Clean and maintain your system on a regular basis
• Maximise your evaporative air conditioner's settings

Clean and maintain your system on a regular basis

Get an annual service each summer

Get an annual summer start-up service from an authorised air conditioning service provider. They can check for leaks, remove any salt build up, set the optimal bleed-off rate, and clean or replace your filter pads. It’s the best way to ensure your air con continues to work effectively and reduce your water use. Use our search tool to find a waterwise plumber near you.

Clean the filter pads

Regular cleaning is key to an efficient evaporative air conditioner. Filter pads can get clogged over time by dust, dirt and debris, decreasing your evaporative cooler’s performance. Check the operating manual or call a professional for instructions on cleaning your system’s filter pads.

Maintain flow control

Evaporative air conditioners drain off water while in use, as a bleed-off or a dump style drain. This is to reduce the build-up of impurities to control the water quality. Running your air conditioner at the correct bleed rate can help you save on your water bill while still enjoying a cool and comfortable home.

To keep the pads in good condition, your evaporative air conditioner should have a 'bleed' rate of 11 to 20 litres (based on the specifications of your system). That's enough to fill a standard 375mL drink can in a minute.

Newer, more water efficient air conditioner bleed rates can be as low as 3 litres per hour. Contact an authorised service provider to check your bleed-off rate is set to the minimum required for your system.

How to check your bleed-off rate

1. Put a bucket under where your air conditioner drips or at the end of the bleed-off hose.
2. Check how much it has filled up after 30 minutes.
3. After 30 minutes, an efficient air conditioner would only half fill a bucket. This is around 5.5 litres, or 11 litres per hour.
4. If the bucket has overflowed, the bleed rate could be too high. High bleed loss can also be due to a faulty ball valve that needs adjusting or replacement. This is like a running toilet, but out of sight on the roof. Contact your air conditioning supplier, technician, or plumber for advice. Find a waterwise specialist near you with our search tool.

Note for Kalgoorlie residents: If you re-use your bleed water, put a tap on the hose. Bleed hose sprinklers are common practice in Kalgoorlie. But they can lead to flow rates being much higher than they need to be to maintain the AC units.

Maximise your evaporative air conditioner's settings

Use the 'fan only' setting

Switch your AC to the 'fan only' setting for 2 hours during the day and night as well as on humid days. It will make a big difference in your water use. Besides, fan only is recommended for humid days to prevent turning your home into a steam room.

Set the timer to turn off at night and when you're away

Does your AC unit have a timer? If so, set it to switch off when you go to sleep or in the early hours of the morning to avoid unnecessary use. Also, make sure to turn your air conditioner off when going on holidays to avoid wasting water and power.

Keep windows and doors opened

Open your windows and doors (where possible) in rooms getting cooled to allow air to flow freely outside. Having insufficient openings will reduce the cooling effectiveness of your AC. It can also put too much pressure on the fan.