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Hardscaping 101: Natural Swimming Pools

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Hardscaping 101: Natural Swimming Pools

February 22, 2018

Did you ever swim in a natural swimming pool? There’s no chlorine, no chemical taste or smell, nothing to sting your eyes. Recently architect Alan Barlis, who designed one for a client in New York’s Hudson Valley, described the experience like this: “Incredibly blissful. Once you swim in one of these things you feel like you’ve been so refreshed. It’s like being in a Brita for an hour. It’s like taking the best shower of your life.”

It sounds as if we all should be swimming in natural pools, for our health and the environment’s. So why aren’t we? For one thing, natural swimming pools cost more to install (on average 10 percent more than conventional pools, says an industry spokesman). Perception is another problem, because some swimmers equate chlorine with cleanliness. Finally, a lack of uniform guidelines and rules in the US may make the idea of installing a natural swimming pool seem, well, murky.

On the other hand: incredibly blissful. 

So read on for everything you need to know to decide whether a natural swimming pool is for you.

What is a natural swimming pool?

In Switzerland near Lake Lucerne, a natural swimming pool supported by a retaining wall on a steep slope &#8\2\20;appears to almost float weightlessly out over the valley,&#8\2\2\1; the designers say. Photograph courtesy of Biotop.
Above: In Switzerland near Lake Lucerne, a natural swimming pool supported by a retaining wall on a steep slope “appears to almost float weightlessly out over the valley,” the designers say. Photograph courtesy of Biotop.

Think of a natural swimming pool as a chlorine-free zone. Instead of relying on chemicals to keep the water clean, natural pools have water gardens with plants that naturally filter and clean the water.

Industry pioneer Biotop, headquartered in Europe, has installed more than 5,000 natural swimming pools worldwide during the past three decades and is hoping to make more inroads in the US with its Biotop USA subsidiary. Other industry players include Ensata in the UK, Bio Nova, and Total Habitat.

How does a natural pool work?

A natural pool at Plane Trees Lodge in Australia has a water depth of 6 \1/\2 feet. Photograph courtesy of Biotop.
Above: A natural pool at Plane Trees Lodge in Australia has a water depth of 6 1/2 feet. Photograph courtesy of Biotop.

A natural swimming pool usually is designed as two zones of roughly equal size, separated physically by a submerged or hidden wall that blends in with the surrounding landscape. One zone is for swimming and on the other side of the wall is a water garden. To create an effective environment for cleaning the water, Biotop recommends that a pool be no smaller than 30 square meters (roughly 322 square feet).

What about algae, muck, mud, and other icky things?

Because the swimming zone and water garden zone are separated by a wall, there is no mud or muck in the swimming zone.

Aquatic plants in the water garden zone will remove nitrates and lower phosphates, preventing algae buildup. A layer of gravel at the bottom of the water garden also acts as a filter.

“With the water garden, we are mimicking the conditions you would find naturally in a high mountain lake, so clear and beautiful and with very little algae or anything growing in it,” says Tristan Fields of Biotop USA. “In that environment, the water has a lot of little microorganisms and a wetland that cleans it.”

What grows in natural pool’s water garden?

Stepping stones appear to float alongside a collection of water lilies in a natural pool designed by Ensata in the UK. Photograph courtesy of Ensata.
Above: Stepping stones appear to float alongside a collection of water lilies in a natural pool designed by Ensata in the UK. Photograph courtesy of Ensata.

Depending on where you live, the specific varieties of aquatic plants will vary. But in general you need three types: floating plants (such as water lilies), emergent plants (such as grasses and rushes), and underwater plants (which add oxygen to the water). In addition to plants, the water garden serves as a habitat for beneficial organisms such as water fleas and microscopic zooplankton, which help clean the water.

How much does a natural pool cost to install?

A perennial meadow is in full bloom in late August at the edge of Will and Sarah Murch&#8\2\17;s family pool at Ellicar Gardens in Gringley on the Hill near Doncaster, England. Photograph courtesy of Ensata.
Above: A perennial meadow is in full bloom in late August at the edge of Will and Sarah Murch’s family pool at Ellicar Gardens in Gringley on the Hill near Doncaster, England. Photograph courtesy of Ensata.

A natural swimming pool costs about 10 percent more to install than a conventional swimming pool, Biotop estimates. But over time, there are cost savings: no chemicals and no regular pool-maintenance crews. (The average annual cost of maintaining a conventional swimming pool is about $250, according to home-improvement site HomeAdvisor.)

What maintenance does a natural pool require?

 For more, see Architect Visit: A Natural Pool in New York&#8\2\17;s Hudson Valley. Photograph by Reto Guntli, courtesy of BarlisWedlick. 
Above: For more, see Architect Visit: A Natural Pool in New York’s Hudson Valley. Photograph by Reto Guntli, courtesy of BarlisWedlick

Maintenance is more like gardening than anything else. Take care of water garden plants by trimming them and replacing them, as needed. In springtime, you also may need to remove sediment that accumulates at the bottom of the water garden.

What happens in winter?

Another view of the Murch family natural pool shows the natural pond-like shape of the pool&#8\2\17;s perimeter, softened by grasses that are part of the filtration system. Photograph courtesy of Ensata.
Above: Another view of the Murch family natural pool shows the natural pond-like shape of the pool’s perimeter, softened by grasses that are part of the filtration system. Photograph courtesy of Ensata.

In winter, cut back plants as you would in any garden. There’s no need to drain the pool.

For more tips and design ideas, see our curated guide to Swimming Pools 101, and for more of our posts on natural swimming pools, see Water World: A Natural Swimming Pool, Lily Pads Included and Architect Visit: A Natural Swimming Pool and Passive House in New York’s Hudson Valley.

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