A natural swimming pool is a beautiful and healthy alternative to a conventional pool. By building a natural swimming pool, you are creating a self-cleaning water system that benefits both people and local wildlife, with no risk of releasing chemicals or pollution into the atmosphere, local waterways or environment.
Natural swimming pools use no chemicals or pesticides to maintain the water quality, a welcome relief for those who suffer skin allergies or sensitivities. Through the use of plants and a small aerator, the water ecology is regulated and filtered to keep it clean and healthy.
There are hundreds of ways to build a natural swimming pool and the techniques and systems you use will vary depending on your circumstances. Generally, a natural swimming pool is divided into the swimming zone and plant zones. Usually the centre is for swimming, and the shallows for plants and animals to filter the water.
The plant zone is usually an equal area to the swimming zone. Plant zones have varied depths so different water plant species and varieties can be used, including fully submerged varieties. The plants and animals condition the water, keeping it clean, while the circulation system gently moves the water around the pool to allow the plant beds to remove excess nutrients.
The circulation system is created during the construction to help the natural filtration process. The addition of an aerator also helps oxygenate the water. Plants and animals maintain the health of the water, oxygenating and filtering, as well as removing the nutrients that would otherwise allow algae to flourish.
Building The Pool
Natural swimming pools can be built cheaper and more ethically than conventional pools, depending of course on the design, site, size, earthworks, cost and availability of materials you wish to use, and the extent of construction work you’re willing to undertake yourself.
There is no set way to build a natural swimming pool. The basic principles can be adapted to many different designs and budgets. There are three main methods of construction to choose from: a rubber liner, concrete or clay base. The materials, plants and filtration system can be different depending on your desired outcome and budget. When considering the design and construction, there are so many options. Having a final plan and estimated budget (along with knowing the building process stages) makes it much easier to stick to the plan.
When deciding on water plant species, consider not only which varieties you like but which are best suited to your area and climate. It is important to remember that many water plants can spread, take over and enter natural waterways, so researching varieties that work for your situation is vital to a low-maintenance system. We chose mainly native water plant species with some exotics. These included assorted water lilies such as water iris, Japanese and Louisiana, several varieties of rush including variegated club, and dwarf papyrus, ribbon grass and water plantain.
Like all pools, a natural swimming pool requires regular maintenance. You’ll need to remove dead foliage, leaves and flower heads from the plant zone, and divide plants as needed. The leaf skimmer needs to be emptied regularly and the filter in your pump system will also need cleaning. There’s more maintenance required in summer as there is more plant growth and warmer water temperatures. Cooler water means less algae and therefore it is important to have a deep zone in your pool for cooler water.
In regard to adding fish and aquatic life to your pool, this is a personal choice. A natural swimming pool does not require fish species to be added, as frogs and other life will find your pool and establish their own balance. Fish and other aquatic animals also add nutrients to your pool, so your pool should be large enough for the size and amount of aquatic life you had in mind.
Natural swimming pools require a lot of water to initially fill and then refill the pool. It is important to look into this when designing your pool. The water level will need refilling regularly; each week or fortnight depending on the amount of evaporation, especially during a hot and dry summer. We were forced to delay the construction of our natural swimming pool until we had saved for and installed a pump from the river to our house, 2 km away.
It is very important to look at the cost and availability of the materials you wish to use to build your natural swimming pool. For example, purchasing and importing large amounts of stone can soon blow out a conservative budget. In our natural swimming pool, we used an extensive amount of natural rock and stone in the design. Consequently, we decided to undertake additional earthworks on our property, so this gave us the most cost-effective way to get such large pieces on site.
With the natural swimming pool design complete, the earthworks can go ahead. We were lucky enough to own our own bobcat. This meant that we could complete the final shaping earthworks ourselves and finish the stonewall of the pool.
Forming up and pouring the concrete edging around the perimeter sets the level of the pool. Other materials can be used for this, such as rock or wood, or you may be converting an existing dam or water feature. Installing an ag pipe drain ensures that no runoff rain or water enters the swimming pool, which can cause extra stress on the system.
With this completed, you can then lay second-hand carpet over the entire base of the pool area, followed by a Geotech fabric layer that protects the liner from being punctured. We chose to use a EPDM rubber liner, which was one of our most expensive costs. Our liner weighed around 500 kg and our site was quite challenging, so with the help of our bobcat and an additional eight or so friends and family, we unrolled and spread out the rubber liner. You can avoid all this by having a natural earth bottom to the pool, but it will be more like a dam and not clear like a traditional swimming pool.
Internal walls that separate the plant zone areas from the swimming area need to be built. Great care needs to be taken to ensure that the liner is not damaged. These walls can be built from stone, timber or sandbags, to name just a few. We built a colossal stone wall 20 metres long that gradually grew in height from 1.6 m to 3 m on the inside of the pool. The construction of a second stonewall on the opposite side of the swimming region was built for a smaller plant filtration zone. Once these walls were completed we filled them from behind with river stones and sand.
The filtration system should now be installed. For us this included a skimmer box that removes leaves from the surface of the pool, and a pipeline for the pumping system running through the entire plant zone area. This sits between 50 mm river stones, layers of Geotech fabric and river sand. Between each layer of substrate material is a layer of fabric that prevents them from mixing. These areas will be used for plant zones.
Many natural swimming pool designs choose to leave the liner exposed, but we chose to cover the entire base of the pool in river stones. If adding stones on top of the liner, first add another layer of fabric for protection.
Once the water level reaches the top of the dividing stonewalls, add the water plants into the sand of the plant zones areas. Fill the pool until the water level reaches around 50 to 100 mm from the surface. More water plants can be added later.
Filling The Pool
Once constructed and newly filled, natural swimming pools take time to settle and clear. Having the pump on for regularly intervals each day is best. Drawing or pumping through the plant zones and through the skimmer quickens the process.
Building a natural swimming pool has been a wonderful and satisfying experience for our whole family. We have spent an incredible summer enjoying our water oasis during such a hot and dry season. There is an abundance of dragonflies, butterflies, frogs and birds. We have never seen Azure Kingfishers here before and we now have them diving in and out of our natural pool, just outside our front door.
Natural Swimming Pools: A Guide for Building by Michael Littlewood. (Schiffer Publishing Ltd 2006)
Shona and her husband Barlo live in Upper Brogo, NSW, with their two daughters. They run a carpentry and joinery business specialising in recycled timbers and sustainable building. They are now building light footprint, eco friendly, contemporary tiny houses. For more info email firstname.lastname@example.org or visit www.sowelo.com.au.