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The natural swimming pool offers the pleasure of bathing in clear water in the heart of a real aquatic garden. An ecological environment where plants guarantee the quality of untreated water chemically.

Bathing in the untreated water of a natural pool

The design of the drain under the natural pool

If after a study, a drain proves useful, it is necessary to "overlay" the bottom of the bathing basin by 50 cm to place the drainage system.
This consists of a geotextile film placed at the bottom of the pit, a drainage pipe (Ø 80 mm) arranged in curves of large radii on the geotextile and another drainage pipe around the periphery of the trench. swimming pool.
The whole is filled from the bottom up with the help of pebbles (granulometry 3 to 6 cm), then of gravel and embankment. The geotextile is then folded down to prevent the earth from clogging the drain. The evacuation is carried out in a ditch below, in a lost well or in a decompression well equipped with a pump (with automatic start by float).

A water garden to bathe

The so-called natural pool is nothing like a traditional pool. The concept is closer to an aquatic garden in which it is possible to bathe. Although the water receives no treatment (chemical or ultraviolet), everything is natural and alive: microorganisms are not "killed", on the contrary. No more red eyes and allergies!

The pool looks like a real natural corner. Some varieties of plants grow there and swimming is also shared with small fish (white only). The water is crystal clear, like all the rare rivers and mountain lakes that are not polluted by nitrates and pesticides.

But nothing obvious! A natural pool must be thought according to a strict specification. This approach creates a favorable environment in which water regenerates naturally.

Self-cleaning in a natural pool

purification of water in a natural pool

Developed and patented by the company Bioteich, the "Natural bathing" process preserves all its clarity with water through a physical self-purification, bacteriological and biological.

To obtain such a result, the water circulates in a closed circuit. It passes successively from a cascade (for oxygenation) to a pool of regeneration before arriving at a bathing pond. There, a conduit directs it to a settling column which ends in a filtration basin. A pump feeds the circuit.

settling column and filter pond of a natural pool

In concrete terms, the two basins (one for swimming and the other for filtration) are connected by a decanter. They are filled with drinking water. The principle of operation is simple: the bathing water is sucked into the decanter where the heavy particles (those that can not be absorbed quickly by the plants) remain in the bottom.
Then, the water rises in the column of the decanter before being released into the filtration pond where are planted aquatic plants that act as a filter. Purified, the water is then pumped to feed the oxygenating cascade. Finally, it is sent back to the regeneration basin, which gently pours it back into the bathing pond.

The circulation pump (with special filter) runs continuously. It guarantees the quality of the water by avoiding any stagnation. In case of failure or short-term stop (for maintenance, for example), you do not risk to see impurities, even in summer. If nevertheless micro-algae develop, they will disappear as soon as the circuit is put back into service: the treatment is provided by the bacteria (99.9% of them are not dangerous for health).

Be careful, this process does not treat dirty water! It only helps maintain the initial cleanliness. This is why it is best to fill the basin with tap water. Rainwater is discouraged; as for spring water (not always clear), it is only usable in case of deep drilling.

Natural Pool vs. Classic Pool: More Space

The design of these pools requires two to three times more space than a conventional pool. Here, 70 m2 of water surface are needed for 30 m2 bathing. With this requirement, they can be implemented in all terrain configurations. It is nevertheless preferable to accompany the process of a reflection on the configuration of the garden. This concept is difficult to envisage without the support of a professional to successfully integrate bathing.

Like traditional swimming pools, the implementation begins with the earthworks: digging the bathing pools, filtration and regeneration (which adjoins the first). The perimeter of the regeneration and filtration unit is delimited by a concrete belt. Depending on the configuration of your land, you may need to make a drain to collect seepage water around and under the pool area. A useless step on this site but which should not be neglected, especially if a doubt remains as to the nature of the soil (see: "the design of the drain" at the end of the article).

The swimming pool is then made in the same way as a swimming pool. All the techniques are conceivable: self-assembling blocks (as here), but also shotcrete or wooden structure. Concrete remains the least expensive solution.

Swimming pool waterproofing membrane

Once the shell is finished, a geotextile (non-woven felt) is placed at the bottom of the bathing, filtration and regeneration basins to ensure the protection of the waterproofing membrane covering it. Made of flexible and recyclable polyolefins, this membrane is environmentally neutral. Welded with hot air, it has good mechanical performance combined with great flexibility (so it can adapt to all forms of basin).

Green in color, this membrane is visible in the bathing pond and covered in the regeneration basin by pebbles and in the filtering basin by a filtering complex (pozzolana, pebbles, gravel rolled in successive layers and filtering elements). Before the impoundment of the two basins, specific plants are planted. They are of two kinds: purifiers (rushes, iris or phragmites) or decorative (papyrus, lotus, water lily and mint).

A simple reheating

It is possible to heat or rather to heat the bathing water (as for a conventional pool). Before even thinking about a heating mode, keep in mind that water can naturally and quickly rise in temperature thanks to the sun. Shallow depth (up to 60 cm) and lined with pebbles, the regeneration basin ensures part of the warming of the swimming pool.

All the usual heating means are possible. Even if, with this type of process, it is better to resort to solar or geothermal heating, environmental protection requires.

Be careful, it is not a question of heating the water at 25° C in April: the vegetation will not support it. This is why we talk about warming rather than heating. In fact, the increase of the water temperature of the basin must never exceed 5 or 6° C. For example, if the water is at 18° C in June, the temperature can not exceed 24° C once warmed.


This aquatic space requires a minimum of maintenance (identical to that of a swimming pool): passage of the robot to clean the swimming pool, cleaning of the beaches, skimmers and the filter of the pump. To which is added, as for a garden, the maintenance of aquatic plants. It consists mainly of folding them (shorten) at the end of the season and to prevent any anarchic development.

Small green algae can appear: remove them by hand. Do not use chemicals that would jeopardize the natural balance of swimming. The decanter tank must be cleaned every five years. And every year, it is necessary to "reseed" bacteria to ensure good water quality.

The budget is at the top of the range, at the height of the project! It includes all the services necessary for the realization of natural swimming, from earthworks to impoundment. That's about 600 € per square meter of water. An additional budget is sometimes necessary for the landscaping of garden areas and wooden terraces.

Not to mention, of course, the anti-convoy safety system for young children (alarm or fall protection barrier) which, let us remember, has become an obligation.


terracing for natural pools

After the study of the land, the earthworks are carried out respecting the depths: the surroundings, the basins areas (1.60 m) and the trench between the bathing pond and that of filtration.

The bathing basin

swimming pool of a natural pool

The bottom of the swimming pool is prepared for pouring the slab. The quality of the concrete and the reinforcement determine its solidity. The reinforcement consists of welded mesh (Ø 3 mm and mesh 15 by 15 cm).

Bathing in clear water with a natural pool: natural

The slab (20 cm thick) is only used for the swimming pool. It is executed with a concrete delivered in truck ready for use dosed at 350 kg (cement) / m3 (of concrete). Installed before pouring, the bottom drain is protected.

Bathing in clear water with a natural pool: clear

The first row of formwork blocks (in hollow hollowed out box) is made on the slab. The rebars are set up as and when. The use of chalk and plumb bob is essential to obtain a perfect level.

Regeneration and filtration ponds

filtration pool of a natural pool

Next step: the installation of the concrete border that delimits the perimeter of the aquatic garden (delimitation of the regeneration and purification basins). It is also at this moment that the waterfall is realized.

geotaxtile for swimming pool of a natural pool

A geotextile (non-woven felt) is unrolled over the entire surface of the three basins (bathing, regeneration and filtration). It must avoid punching the waterproofing membrane that will cover it.

waterproofing membranes of a natural pool

The waterproofing membrane is first laid on the bottom of the bathing pond. Based on synthetic polymers, it is fully recyclable and insensitive to chemical attack while being very resistant.

heat sealing the waterproofing membrane of a swimming pool

Outside the bathing pond, the regeneration basin is also sealed by laying the membrane on the geotextile. The welds are made by heat sealing.

to protect the waterproofing membrane of a swimming pool

In the regeneration and filtration basins, a second (more rigid) geotextile is installed on the waterproofing membrane to protect it.

The filtration basin: setting up the filter

decanter and filter of a natural pool

The decanter has been set up under the filter basin. Only the exit is visible (concrete nozzle). It will be hidden later among the filtering plants. Before this step, the pond is filled with the filtration complex.

The regeneration basin filter

delimit the swimming area of ​​a natural pool

To delineate the bathing area, the concrete border is crowned by wooden beams secured to the shell by pegging (it is possible to provide a stone belt).

regeneration pool of a natural pool

A first impoundment makes it possible to check the tightness. Covered with pebbles, the regeneration basin begins to be planted. Plants are set dry on a specific substrate.

natural pool plants

The regeneration of water is ensured by the plants which also contribute to the natural aspect of the aquatic garden.

Integration in the garden

natural pool pontoon

Once the plantations are finished, the whole aquatic garden is put in water. Built in rot-proof wood, the pontoon provides direct access to the bath, passing over the regeneration zone.

natural pool waterfall

The return of water in the basin can be made by a cascade made of stone country. Other more discreet solutions are conceivable, such as simple nozzles.

aquatic garden of natural swimming pool

For the project to be complete and homogeneous, the creation of a link between the aquatic garden and the garden itself contributes to its integration into the site. In all cases, swimming is part of the garden.

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