Swimming ponds


Wednesday, 27 November, 2013



Swimming ponds

A natural swimming pool, also known as a swimming pond, is the union of a swimming pool and a water garden. Pool+Spa discusses the concept of swimming ponds with Jeff Knox from Riverwater Pools.

After running a landscaping business and working with pool builders for over 15 years, Jeff Knox, originally from Melbourne, started a new landscaping company in Albury. With an emphasis on ponds and water gardens, Knox saw his interest move towards healthy ponds.

“I had gained a good amount of knowledge regarding the requirements for creating healthy ponds and had considered the potential to use the Firestone EPDM rubber liner for a conventional type of pool,” said Knox.

It was then that a supplier suggested he look at the website of a European ‘natural swimming pool’ builder.

A natural swimming pool, also known as a swimming pond, is the union of a swimming pool and a water garden. Knox found himself with the ability to apply all of his accumulated knowledge and building skills to a new, totally unique product.

“The unlimited design potential of these pools had a huge impact on me. I started researching everything I could possibly find relating to these pools. I was soon up to my ears in aquaculture, aquaponics, fish ponds, water gardens, the nitrogen cycle etc.

“There are now many thousands of these pools across Europe, particularly in Germany and Austria. They are also popular in the UK and are gaining a lot of attention in the US. There are even public natural pools in Germany and Austria.”

In the construction of these swimming ponds, a waterproof membrane or liner is used. The most common in Europe is welded PVC; however, Knox prefers to use Firestone EPDM rubber liner, which he believes will last a minimum of 25 years in the harsh Australian conditions.

Because a liner is used, construction techniques vary considerably from very basic to engineered structural walls made from sprayed concrete, or concrete footings with block construction. It all depends on the structural requirements of the site and, of course, the client’s budget.

“Generally speaking, low-powered pumps are used because the water is not being forced through a conventional sand filter, which takes considerable power.

Conventional sand filters are not used because they could potentially harbour pathogens. Most natural pools use no conventional fine filtration, instead relying on plants to ‘catch’ smaller particles,” said Knox.

Some natural pool builders do use fine filtration, which provides clearer water and prevents blockages occurring in the gravel biofilter. Natural pool pumps need only 25% of the power used by conventional pools; however, the pump generally needs to run 24 hours a day, particularly through the swimming season.

According to Knox, as far as litres pumped per watts consumed, natural swimming pools and swimming ponds are streets ahead. “I have used pumps that consume only 100 watts of power on a 65,000-litre system, connected to stand-alone solar power systems.

“My own pool at 230,000 litres, and my most recently constructed pool at 290,000 litres, each use a single 460-watt pump, less than 0.5 hp.”

A natural pool or swimming pond should have no chemicals or additives put in the water at any time. The water is totally unsanitised, yet a well-built system will produce drinking-quality water. Knox believes that natural pools and swimming ponds are the only true ‘non-chemical’, ‘non-sanitised’ living water pool. “All other systems that ‘claim to be chemical free’ rely on sanitising the water in one way or another. The end result is biologically dead water.

“A well-designed system never requires the addition of any chemicals or additives of any description. To do so is a failure in my opinion. A well-designed system will continue to produce high-quality water as long as the pump continues to run and the system continues to function as intended. Systems that fail biologically will do so because of poor design that allows blockages to occur.

“Albury Council recently assessed the water in my own swimming pond and based their assessment of my pool water on the EPA’s Yarra Watch program (www.epa.vic.gov.au). The EPA (environmental protection agency) says that river water with an E. coli count of 200 (or less) organisms per 100 mL of water is ‘high quality’. My pool water test returned a result of 3 organisms per 100 mL.”

The need to clean these pools and the ability to do so depends on the design of the pool. It also depends on whether a vacuum facility is part of the design. Pools that look very ‘pond like’ can accumulate leaves, algae, dust etc without looking dirty. This debris becomes part of a thriving ecosystem and is not a concern in a pool that is used for placid bathing. However, it could become an issue if the pool was used by many playful bathers stirring it up. Pools that look more like conventional pools need to be vacuumed to maintain good appearance.

The natural ecology that will take up residence in a well-designed system is what keeps the water healthy, just as in natural mountain streams.

There are many plants that can be grown in a natural swimming pool. Australian natives including bottlebrush, tea tree and river-bank grasses can grow successfully. There are also reeds, Murray River Red Gum and Swamp Oak. The types of plants that can be grown also depend on the design of the pool. The general idea is that plants are placed bare rooted in gravel and take all their nutrients from the water.

Natural swimming pools are more often two separate bodies of water. One is for swimming and the other is for the biofilter/planted region, and nutrients are removed from the system by means of fine filtration and vacuuming. This leaves less nutrient for plants; however, the water quality and clarity is generally higher. The separate swimming area is also easier to keep clean and there is much less for swimmers to stir up. A better choice for lots of playful kids.

Natural swimming pools and swimming ponds can provide an excellent habitat for any creature that lives in and around fresh water. Fish can be put in these pools but careful consideration is required as to what type and how many. Fish will eat many of the inhabitants if they have access to them. Frogs will be most at home in planted areas and birds will drink from the pool. Ducks are not welcome because they poo in the water and around the pool. A net may be required to prevent ducks taking up residence in spring.

“I have built two pools for active families with young children and two pools for adult couples. The common interest amongst my customers is that natural pool water is ‘real living water’ that will sustain any aquatic animal or insect. These pools basically mimic the biological conditions in nature that produce the highest quality water.”

Natural swimming pools and swimming ponds are considered swimming pools and are therefore required to conform to the same regulations as conventional pools. They are not ‘ponds’ and can only be built by appropriately licensed people, that is, pool and house builders. Swimming ponds can be designed and built to suit urban areas, as well as country areas.

“The design potential is very exciting, as these pools are mostly built using waterproof membranes and are not subject to size limitations. Anyone considering a natural pool/swimming pond is strongly advised to see operating systems built by their proposed builder. Although the concept is extremely simple, delivering this concept in a well-working construction is much more difficult. A failed natural pool/swimming pond construction will result in a green swamp.”

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