How to 'green' your backyard pool

G Magazine

Worried about the environmental impact of your backyard swimming pool? Slip on a pool cover, slop in some rainwater and slap a solar array on your roof.


Credit: iStockphoto

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While swimming is a great form of exercise, the downside is that pools require vast amounts of water. Just to fill the average backyard pool takes 50,000 litres- and that's roughly one third of the water used by an average person in a year.

Even more water is needed for regular top-ups. All up, a home with a pool uses 10 per cent more water than a home without a pool.

But surprisingly, water isn't the only conservation concern - swimming pools are energy intensive too. According to the NSW Government, running a pool pump will increase your household energy use by 17 per cent and that's not including energy needed for pool heating.

So does this mean we should drain our swimming pools? Has the backyard pool become an extravagant luxury this planet can no longer afford? Actually, there's a surprising amount we can do to cut down on pool energy and water use.

Slash water wastage

An uncovered pool can lose up to one-and-a-half times its total volume in one year through evaporation. In Sydney and Brisbane, rainfall can come close to replacing half the evaporation, assuming that it falls at the right time and in the right amounts so the pool doesn't overflow. Yet in a dry city like Perth, rain compensates for only 10 per cent of the water lost.

There is one really simple way to save water - invest in a pool cover and reduce evaporation by up to 97 percent. For an outlay of $500 - $1,500 you can purchase a cover that will also prevent heat loss at night, thereby extending the swimming season and saving on heating costs.

As an added bonus, covers also keep leaves and dirt out of the pool and reduce the evaporation of the chemicals used to keep the pool clean.

"The important thing to consider when buying a cover is how easy is it to use" says Manfred Wiesemes, president of the Swimming Pool and Spa Association of NSW. "A cover with a roller mechanism is easier to use."

The type of filter you use can also make a big difference to water efficiency. Sand filters can waste up to 15,000 litres of water each year because they require backwashing to clean the filter. Cartridge filters, on the other hand, can be cleaned with a quick rinse from the hose, saving water and reducing the amount of pool chemicals dumped into the sewer.

Finally, make sure you have no leaks - one drip per second adds up to 7,000 wasted litres a year. To find out if your pool leaks, Manfred Wiesemes recommends the following method:

"Put a bucket on a submerged step of your pool and fill it to the water level of the pool. Leave [it] overnight. If the pool level is lower than the bucket you have a leak."

Top up with rainwater

No matter how vigilant you are at preventing water loss, the pool will need an occasional top-up. A simple idea is to attach an inexpensive rainwater diverter to a downpipe to direct water into your pool. Some models on the market can also prevent the first flush of leaves entering your pool.

Just bear in mind that during a large downpour you may need to divert the flow back to the stormwater to ensure the pool doesn't overflow. A better but more expensive solution is to install a rainwater tank so you can store water for when you need it.

Create a zero-emission pool

It's an expensive exercise to operate your pool pump continuously - just running it for eight hours a day will cost about $650 per year and emit four tonnes of greenhouse gas emissions.

The solution is to purchase a solar pump that will cost nothing to run.

At the very least, use a timer to operate the pump during off-peak times - just be sure to adjust it when the seasons change. And for those using an automated chlorinator, consider updating it with a solar model.

Many pool owners like to extend the swimming season by heating their pool - but how do you avoid puffing more greenhouse gases into the air? The answer is to go solar. "Solar pool heating is the most popular way to heat pools," says Wiesemes. There's a good reason for this - as well as saving on greenhouse gases it will save you a tonne of money.

To get the most from a solar pool heater the NSW Swimming Pool and Spa Association recommend an array covering at least 80 per cent of the pool area that's set up on a north-facing roof.

If your roof is unsuitable, a heat pump is another greenhouse friendly option. Heat pumps work by absorbing heat from the air and transferring it to stored water - a bit like a reverse refrigerator. While they use electricity, the amount required is tiny. Traditionally used for household hot water they are now available to heat swimming pools. Since warm water evaporates faster than cold water it's even more important to cover a heated pool - it will also reduce heat loss.

Also crucial for optimum operation is an easy-to-install solar controller that monitors and regulates water temperature.

Cut down on chemicals

Pools use rather a lot of nasty chemicals - of which chlorine is the most significant. The concentrated liquid form of chlorine, sodium hypochlorite (or bleach), is extremely corrosive and regarded as highly toxic by the US EPA. For these reasons it should be securely stored and kept out of reach of children. It is acutely toxic to aquatic organisms, which is another reason to avoid sand filters, which create high volumes of chlorinated backwash.

The need for chlorine can be minimised through your choice of water treatment system. UV and ozone systems cut down the amount of chlorine needed by 70 to 80 per cent, and ionisers also reduce the need for chlorine.

Salt chlorinators have the advantage that you don't need to handle chlorine although you'll still end up with sodium hypochlorite in the pool solution.

You can also reduce chlorine use by keeping your pool clean and preventing its evaporation with a pool cover. Avoid locating plants that drop their leaves close to the pool and ensure filters are cleaned regularly. To avoid chemicals altogether consider a natural swimming pool.

The upshot?

Pools may be an unparalleled summer luxury - let's face it, there's nothing quite like a midnight dip on a hot summer night - but they are certainly not the eco-friendliest addition you could make to your backyard.

If you are going to have a pool, there are ways to make yours the greenest in the neighbourhood. With rainwater and solar power, you can reduce your pool's impact to near zero.

Of course, for those of us lucky enough to live near the sea, a river, lake or mountain stream, nature provides the greenest swimming pool of all.

Tips: before you construct a pool

1. If you're in the designing stage, go for a free-form pool as it generates more efficient water circulation, cutting down on energy needed for filtration.
2. Plant drought-tolerant native plants and create windbreaks with bushes and trees to reduce water evaporation
3. Have the company dig a hole for a rainwater tank to go beneath the pool so the water is topped up when it rains.
4. Choose the pool location wisely - opt for a sunny position that passively heats the pool, cutting down the need for artificial heating.