Building a natural swimming pool

Last updated Monday 5 January 2009

If you're planning on building a swimming pool, ever thought of making it a natural one?

Swimming pools have a bad reputation as major sources of CO2, but you can now put in a natural pool for the same cost as a traditional concrete version.

Contrary to popular opinion, pools don’t have to be 'natural' to be eco-friendly. Pools with solar panels and heat pumps have been available for decades. But natural pools still come up trumps, because they avoid new concrete which is one of the most CO2-intensive building materials you can use. Better still, they let nature do the dirty work. In natural pools, aquatic plants are used to clean the water instead of electrically-powered filters and chlorine. Not only have these plants evolved an extraordinary degree of efficiency over billions of years of evolution, they also do it free of charge. By going natural, you use less energy - and create less CO2 - constructing, pumping and filtering your pool.

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It's Not Easy Being Green: natural swimming pools

Lauren Laverne takes a dip in an eco-pool

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What difference will it make?

A natural pool doesn't require an electrically-powered UV filter. It uses aquatic plants to filter the water instead.

The electric pump for a natural pool uses 75% less energy than the pump for a traditional pool. (You can even turn it off at night when the plants are 'sleeping'.)

The average concrete pool uses approximately 70 tonnes of concrete, one of the most CO2-intensive building materials. (About 130kg of CO2 are emitted per tonne of concrete.) Building a natural pool using recycled construction materials can cut your emissions by about ten tonnes of CO2 (the average Brit’s annual emissions).

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What's stopping me?

"They are more expensive to build aren’t they?"

At 450 per square metre, a professionally installed natural pool costs about the same amount of money as a regular pool. You can do it for less if you build it yourself, and the running costs may ultimately be cheaper because you use less power over the lifecycle of the pool and won't need chemicals like chlorine.

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What's the debate?

"Are pools really all that bad for the environment?"

If pools were Hollywood stars, these 'eco-baddies' would probably have clipped English accents and an evil demeanour. But the Swimming Pool and Allied Trades Association argues that pools are actually the green movement's unsung heroes. Energy-saving technologies like the heat pump and solar-powered covers have been championed by the pool industry for decades.

Pub Fact

  • There are 300,000 pools in UK gardens
  • About 100 natural pools have been built in the UK so far
  • One of the biggest public man-made natural pools in the world, measuring 5,000 square metres, was completed in Lindenthal near Leipzig in Germany in 1998
  • An Olympic-sized swimming pool contains one million litres of water
  • One school in Northamptonshire recently slashed its CO2 emissions by 50% by installing a state-of-the-art heat recovery and dehumidification unit in the school swimming pool
  • Concrete is the second most commonly used construction material in the world
  • Cement, a principal ingredient of concrete, accounts for at least 5% of global CO2 emissions

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How will I do it?

It's possible to build a natural swimming pool yourself. Here's a rough guide.

Dig it:

  • To stop slippage or cave-ins, dig sides that slope. Aim for a one foot vertical drop for every three horizontal feet
  • Reserve about half the pool for aquatic plants. You can either group the plants at one end or dedicate the pool's entire border to them
  • Line the hole. For ornamental pools, bentonite clay is a low-impact liner, but if you plan to splash around then you need more robust lining made from recycled construction materials or rubber
  • Choose your plants and anchor them in gravel, for example, sedges, rushes, lesser cattails, pickerel weed, arrowhead, water primroses, common waterweed, hornwort and aquatic irises. Ask for varieties that won't overcrowd other plants

Keep it clean:

  • Monitor your pool's progress. It will take some time to get the balance of plant life and nutrients right
  • If an algal bloom strikes, try adding more plants or straw, and increasing aeration
  • Check your pumps annually and clean out plant debris a couple of times a year
  • No need to drain the pool – simply top up the water level from time to time
  • You could also consider using a heat pump to heat your pool's water or solar panels to power the pump

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