Natural swimming pools

A thriving habitat for wildlife, a haven for natural planting, and chemical-free swimming — here’s what to know about going au naturel

Ask people for a list of things they’d love in their garden and a swimming pool is always on there. A relaxing dip in your own pool, in your own garden is an idea that appeals to many. One concept that is becoming more popular in the UK, following on from long-standing trends in mainland Europe, is the idea of a natural swimming pool. Chemicals are not used to clean the water; instead natural swimming pools are filtered using aquatic plants, which clean the water naturally.

What are the options?

Natural swimming pools – which can be as small as 15m2 – come in two main forms: the traditional natural pool (or pond), and the living pool, which visually looks more like a traditional filtered pool.

THE NATURAL POOL

With a natural pool, the idea is that a large, deep pool – the swimming area – is surrounded by marginal planting that filters and purifies the water naturally. In essence, this type of pool has the look and feel of a large pond.

Construction involves creating a reinforced, lined swimming pool area, alongside a series of filtration beds made again with a liner and a series of planted shingle pools, which help to remove debris. Unlike a traditional pool, a natural pool’s feel is best maintained by dark green liners. As its filtration system relies entirely on plants, there’s no option to artificially heat the water, and using a darker liner will give some secondary warming that the light blue or aqua liners of a traditional pool don’t. You can also install lighting both in the main swimming area and through the marginal filtration beds.

THE SHAPE The swimming area of the natural pool can be informal in shape or more rectangular. A natural pool can take up quite a bit of space and like any pool, needs to be constructed on a level or levelled site. For a pool with a swimmable area of 20m2 the entire pool would need to be 40m2.this kind of size suits rural locations and those with larger gardens because alongside the pool you will need shallow space for a deck, terrace or jetty access point.the pool area will also need to be planted to merge with the herbaceous and shrub planting that outline the margins of the pool.

THE MARGINS Often the two zones, the swimming pool and the filter beds, are separated by a shallow band of stone.this separation can be given a natural feel, or a more contemporary one (using a band of cut stone, for example). Either way, this band stops the soil of the planted filtration beds moving into the main body of the pool. It is usually positioned roughly 50mm below the surface and should be 100mm to 200mm in width.

One of the advantages of a natural pool is the shallow planted margins that form its natural filters. Rather than the traditional drop into water, the margins on natural swimming pools are sloped. A 20m2 pool, for example, will slope downwards about a metre from the edge to roughly 400mm below ground level (or your set 0 point if you’re building on a slope and are creating an artificial level). The depth of the swimming area will be around 1.5m. So for a 40m2 pool the shallow graded margins need to be 20m2 — this will include 7m2 of bio (plant based) filtration and 13m2 of marginally planted space that will allow the water to purify. The swimming area will be 20m2 with a depth of at least 1.5m to allow good swimming and stop plants creeping away from the ledges to the swimming area.

THE PLANTING Planting for a natural pool is key. Of course, like any part of the garden, it will require maintenance — herbaceous aquatic plants will need to be recut back in the late autumn. It’s also worth remembering that the term ‘filtration plants’ can be a misleading one as the plants do not remove particulate matter from the water. What they actually do is absorb and capture nutrients from the water — in turn

GROWING GUIDE

Essentially all plants can be grown organically so the options are endless, but here’s some ideas to start out with:

FRUIT AND VEG

BEGIN WITH: Carrots, potatoes, onions, garlic, leeks, beans, berries.

WORK TOWARDS: Parsnips, celery, cauliflower, aubergine, asparagus, apples.

llORNAMENTALS

BEGIN WITH: Lawns, bulbs, choisyas, sedums, ferns, geraniums.

WORK TOWARD: Dahlias, fuchsias, hydrangeas, clematis, box hedges, roses, pyracanthas (these harder options are susceptible to pests).

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