Natural swimming pools: how to get this summer’s most-wanted garden feature

Expert advice on how to plan your pool to begin enjoying the joys of wild swimming in your own backyard

a pool in the austrian mountains by biotop, which has one area for swimming and another for plants
Lorenz Masser

Imagine the scene: you’re slowly making your way through still water on a sunny afternoon, greenery on all sides, while dragonflies hover overhead. This is the picture painted by a growing class of converts to the swimming pond.

That traditional square of brilliant blue water may be an enduring status symbol, but those in the know are seeking natural highs. A natural swimming pool offers a gentler experience. While the former relies on chlorine and salt for cleaning, these pools let nature do the work by harnessing the biological processes of plants.

richmond bell architects   wiltshire natural pool
Richmond Bell Architects worked with Water Artisans for this natural swimming pool in Wiltshire
Richmond Bell Architects

How to plan your natural swimming pool

Paul Mercer, founder of The Swimming Pond Company, shares his expert advice

What kind of site is best-suited to a swimming pond? The first thing is good access, as you’ll need to get an excavator in to dig the hole. Ideally, you’d position the pool as close to the house as you can, as swimming ponds are such a thing of beauty and can be enjoyed from inside the home even in the depths of the winter months. Think about a spot that’s away from mature trees, as you don’t want lots of leaf debris falling in.

Is there anything else to consider at the planning stage? If you live in a listed building or within a conservation area or an Area of Outstanding Natural Beauty (AONB), then you’ll need planning permission. This is something that we handle for our clients. The planners love what we do and we’ve never been turned down.

natural pool built by austrian will architektur mit weitblick projectphotography by paul ott
The pond at this new home in Austria by WILLL Architektur can be accessed directly from the terrace
Paul Ott

What choices are involved? First, you’ll need to think about size. We tend to discuss the length our clients want to be able to swim, and then work backwards. Depth is important, too, and our pools can go right down to 2.4 metres if you’d like to be able to dive in. We also need to consider how the water is accessed – you might opt for ladder steps, which we make ourselves in oak, or stone steps leading down into the water.

How is the pool natural? Also referred to as the biological filter or planted area, the pool’s regeneration zone is the key to creating an ecological balance. It’s at least one metre deep and made up of gravels and filtration materials, which are then planted with a range of aquatic plants.

decking around natural swimming pond designed by woodhouse natural pools
Decking areas provide spots for sunbathing in this project by Woodhouse Natural Pools
Marianne Majerus

Water is circulated 24 hours a day, with the aim to turn over the whole of the pond’s volume. The bacteria that builds up within the zone breaks down any waste matter that is pulled in through the filter, which means that clean and clear water can be pumped back into the base of the pool.

What does it mean for a pool to be ecologically balanced? In order to achieve crystal-clear and clean water, we need to balance the level of nutrients. It needs to be high enough to feed our plants, but not too high that it encourages blanket weed to grow. The key is getting the balance right in order to create the perfect habitat for a wide array of wildlife.

natural swimming pool at folly point in gloucestershire by butz and klug architects
Natural swimming pool at Folly Point in Gloucester Maine by Butz and Klug Architects
Milicent Harvey

When will it be warm enough to use? Temperatures from the end of May to mid-September average around 21 degrees, and we can easily see 25 degrees during a spell of hot weather. The planted area is only 10 to 20 centimetres deep, so the water warms up really quickly.

It’s like a rock pool on a sunny beach in that it’s shallow, so much warmer than the rest of the sea. We draw that heat down and pump it back into the base of the swimming zone, so it will always be warmer than an unheated conventional swimming pool. It’s very different to swimming in a river or lake!

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