24 kl of water is used by your pool EVERY MONTH – justifiable?

This article from the National Spa and Pool Institute of South Africa sheds some light on how much water your pool uses/looses through evaporation and maintenance. Does this water usage make justifying a pool difficult? Absolutely. Are there ways around losing so much? The poolside tank to recycle pool water is one immediate solution – read below for other useful tips:

On average, homes with swimming pools use more than twice pool, evaporation, backwashas much water outdoors than homes without swimming pools. Many homes have swimming pools, which use a lot of water. This fact sheet provides advice on ways to minimise the water use of arid zone pools.

The climatic conditions of South Africa that create high water evaporation are the same conditions that make a swimming pool so attractive: high temperatures and long summers. The relatively cheap cost of water is also a factor in encouraging households to fill up the pool without much consideration of water loss and water use. However, South Africa is a water poor country and we face severe restrictions around pool use, it is time to take some steps to manage the water use of the swimming pool.


What is evaporation? As we know from boiling water and seeing it turn into steam, a simple definition of evaporation is the process whereby liquid water becomes a gas and dissipates as the water temperature is increased.

During summer, evaporation rates increase and the water level in the pool begins to drop rapidly. In a single day up to 300 litres of pool water can evaporate under the harsh sun, which is about 30 buckets. Over the year almost the entire pool volume will evaporate away if not topped up. Environmental conditions, such as humidity, wind, over-night air temperatures, and higher pool water temperature, all affect the rate of evaporation. The size of the pool is also a factor: bigger pool = more water loss. In different areas the rate of loss varies, but a general figure of 35mm to 45mm per week Refer: (Dr Jeremy Gibberd CSIR) during summer will be a clear indication. This is under normal conditions. Abnormal conditions such as:

  • Heated pools
  • Water features
  • Pools in open windy areas
  • Rim flow pools

Will increase water loss drastically.

Topping Up

Do you know how much water flows from your backyard hose per minute? The average supply is around 17 litres per minute. Topping up the pool everyday or second day in summer can work out to a lot of water: 17 litres x 30 minutes x 30 days = 15, 300 litres a month! Combine this top-up with water lost through evaporation (approximately 9000ℓ per month) and your pool’s water use could be up to 24 000 litres per month.

Check for leaks – increased water loss or needing more chemicals are clues to unseen leaks.

Pool Covers

Pool covers work by insulating the pool water from wind and heat evaporation. Cover the pool in winter and non-swimming periods and lower maintenance costs and water loss all year around. Using a pool cover reduces evaporation by 90 to 95%. Pool blankets and “liquid” pool covers are not as effective but do still reduce evaporation rates by 40+%.

The added benefits of covering the pool when not in use are:

  • Reducing the cleaning time by preventing debris from falling on the pool surface
  • Reducing the amount of chemicals needed to keep the pool clean

Backwash, Cleaning and Draining

Pool maintenance must be done regularly to make sure that the water is safe to swim in, however there are ways to minimise the amount of water needed to clean the filters.

Sand filters are common and require backwashing once every 2 weeks depending on circumstances. Only backwash until the glass goes clear – backwashing for longer will waste excessive amounts of water.

Other filters can be manually cleaned. Cartridge filters are maintained by rinsing out and soaking in solution if needed and only need to be replaced every two to three years.


  • Proper chemical balancing can prevent and cure most water clarity problems.
  • Pools can often go 10 years without draining and refilling.

Waterwise Pool Rules – to keep water in the pool:

  • No bombing or excessive splashing
  • Drip dry on the top step so the water goes back into the pool
  • Ask pool users to top it up with a bucket so they are aware of the amount of water being used
  • Only run pool fountains and waterfalls when you’re entertaining, as they increase evaporation
  • Avoid overfilling the pool: the water level should be about half way up the skimmer box opening for the filter to function properly
  • Think about lowering the water level to reduce losses from splashing
  • Plant or install windbreaks around the pool as even light winds will increase evaporation rates

Compiled by:
GD Snygans

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