Pool covers are becoming more and more popular as they're the best way to reduce dirt and debris getting into the pool as well as saving you hundreds of dollars in excess water bills by preventing evaporation. They're also great at retaining heat to extend the swimming season.
Evaporation reduction is the main benefit of installing a pool cover as an average 8 x 4m uncovered Melbourne pool will lose almost 45,000 litres of water each year and up to 80,000 litres of water each year if it’s heated all year round.
The 4 main factors that affect evaporation rates from domestic outdoor pools are:
Pool surface area
The bigger the pool, the more surface area, therefore, a greater evaporation volume.
The temperature of the water and air
The highest evaporation rates occur when the differences between water and air temperatures are the greatest. Surprisingly this may not be in the middle of a hot day when the pool is in use as at this point in time, the water and air temperatures may be quite close. Whereas, later at night, the pool water may remain warm, but the air temperature has fallen substantially which means a greater temperature difference between the air and water and therefore greater evaporation.
Humidity
As is typical in most parts of Victoria we have relatively low humidity. The drier the air is, the greater the evaporation rate. In very humid conditions less evaporation occurs.
Wind
The other significant factor for home pool evaporation is wind. A gentle breeze of just 11 kilometres per hour can more than double the evaporation rate by removing the insulating layer of warm, moist air directly above the pool surface.
Here are 4 reasons why you need a pool cover:
Saves water
While evaporation rates vary greatly depending on a range of factors including volume of water and location, an average 8 x 4m uncovered Victorian pool will lose almost 45,000 litres of water each year and up to 80,000 litres of water each year if it’s heated all year round. A pool cover will save you money by reducing your water bill by approx. 45,000 litres / year from having to top up from the tap.
Keeps pool water clean
Pulling the cover over your pool after each use will save you a lot of time cleaning out leaves, dirt and other debris that would be blown into the water if it wasn’t covered. This ensures it’s clean and clear when you’re ready to use it.
Reduces chemical loss
Chemically balancing the water is one of the most costly and time-consuming parts of owning a pool. By installing a pool cover, the need for the chemicals such as chlorine and salt can be reduced by up to 50% by preventing the chemicals from evaporating into the atmosphere and keeping them in the water for longer.
Keeps the heat in = Reduces heating costs
The pool cover acts as a barrier between the cold air and the warmer pool water. A pool cover will increase heat retention by up to 75 per cent, reducing CO² emissions and saving on power normally used to run a heat pump, solar or gas system, as the heat they generate won’t be instantly lost. It also means the system won’t have to work as hard, so you can reduce running times and costs.
So how much water am I losing?
According to the official Bureau of Meteorology long term, historical evaporation rates in Melbourne, measured at the airport over our hottest 6 months October - March is an average of 6.4mm / square meter.
This means the Mean Melbourne Daily Evaporation on a 40,000 litre uncovered pool is approx. 205 litres/day!
The cost of topping up
Depending on your water pressure the average backyard hose (according to the NSW Govt.) is approx. 17 litres per minute. So with this in mind, as an example, an average pool in Summer may take topping up for 10 minutes a day, every second day. This would use: 17 litres x 10 minutes x 15 days = 2,550 litres each month!
Ok... how much will a pool cover save me?
If a pool cover is used diligently it will save up to 95% of your water evaporation saving a 40sq/m pool from losing 53,200 litres each year. That's a lot of money saved on water bills! Also, when it does rain, all that water will still go into the pool, effectively topping it up.
You’ll also notice the reduction in your chemical costs, with lower levels of chlorine and no stabilizer needed (if the cover is always on when not swimming), you can potentially save hundreds of dollars each year on your pool chemical spending as well.