If you have been lucky enough to experience a natural swimming pond you will know the feeling that comes from immersing yourself in sweet, soft, organic water. No salt, no chemicals; you are at one with nature. David Pagan Butler has been obsessed with ponds since childhood and always dreamed of making a pond big enough to get into. ‘Whenever I moved house, I would make another pond,’ he says.
Thirteen years ago, his son came back from a visit to a local swimming pool with a rash all over his body – a reaction to the chemicals in the water. This spurred David on to start building a bigger pond at his home near Holt, in Norfolk, large enough for the whole family to swim in. Since then, he has shared his experiences and methods for building a low-cost, low-impact organic pool through video tutorials and courses to encourage more people to give it a go.
‘I want to show this project is hard work but deeply rewarding and completely achievable,’ he writes in his Organic Pools DIY Manual. Researching the work of other swimming pond specialists, David became aware that many of the so-called natural pools had only a token gesture of plants around the perimeter and still needed conventional swimming pool pumps to filter the water, which use a lot of energy. These pools were also very expensive to install. Determined to find a way to make his own pool work on a much lower budget and, more importantly, with a reduced carbon footprint, he began his own experiments to find an alternative system based on a 50:50 planting-zone-to-swimming-zone ratio.
The whole ethos of an organic pool is to work with nature to provide clean, healthy water to swim in, using plants and organisms to condition the water without the need for chemicals. ‘The key to a balanced eco-system is to create a low-nutrient environment and not to let certain species dominate,’ says David. ‘Single-cell suspended algae is the stuff you really don’t want, as it makes the water turn opaque and green, and it thrives when phosphate and nitrate levels are high. What you are trying to do is to minimise the amount of nutrients in the water, so that algae can’t flourish. As the plants grow, they take nutrients out of the water, so the planting zone is critically important in this type of pool.’
The choice of plants does not have to be prescriptive. David prefers to use native plants, such as water mint, flowering rush and water lilies, but you can use any aquatic plants that are not too invasive. Other ways in which nutrients can be minimised is by creating a berm (raised bank) around the pool to prevent soil run-off from surrounding land and to use rainwater rather than tap water to fill the pool. ‘Tap water contains phosphates, whereas rainwater contains very few nutrients and is better for a balanced pool ecology,’ explains David. Over the years, he has developed various Heath Robinson-style systems to divert and pump rainwater from his house and other outbuildings.
However, his main invention has been the bubble system that he uses to help to keep his pool water sparkling clean. This simple device utilises an inexpensive, low-energy aquarium air compressor to aerate the water and also push it round the pond. With a strong liner made of black butyl (synthetic rubber), his 180-square-metre pool has a rectangular, two-metre-deep swimming zone contained by underwater walls and a three-metre sloping planting zone around the perimeter, covered in a sand and gravel substrate. Perforated pipes (available from most builders’ merchants) have been laid underneath the planting zone, so that the water is circulated through the substrate and around the roots of the plants (to help nutrient intake) before being drawn gently into the swimming zone.
David has also designed and patented his Olive biofilter. A floating, bubble-powered filter designed to remove nutrients, working alongside the planted zone, it can be used as an extension of the larger system. ‘The whole thing is very energy efficient,’ he observes. ‘You’re not taking water out of the pool into another area to be filtered – you are slowly pushing it around the pool. It’s like rolling a barrel rather than lifting it.’
This low-key system is much more in tune with nature than a conventional pump. ‘The greatest ally you have in an organic pool is the daphnia or water flea. These tiny crustaceans graze on the algae, so you need to encourage them,’ he says. ‘A conventional swimming pool pump would pulverise them, but this system is much more gentle. A frog could pass through it and not come out with a bruise – it would be like going through a Jacuzzi.’ The entire eco-system of the pool is therefore preserved – from the plants, insects, birds and mammals that use the pool as a life source, to the tiny bacteria and zooplankton in the water: ‘The life of this pond is so complex. Every cubic millimetre is crammed with a whole range of different organisms. Any pathogens that get into the water will be consumed by the battalions of micro-organisms that already exist in the pool.’
David can swim daily in his pool, even in the middle of winter: ‘It is a beautiful place to observe nature throughout the seasons. I swim with dragonflies, damselflies, newts and frogs. Swallows and house martins skim over the surface and pied wagtails hop along the lily pads. I even catch a glimpse of an occasional kingfisher.’
More and more people are finding out about David’s techniques to create a swimming pond for a fraction of the price of a more commercially installed pool. He is happy just to spread the word: ‘If we create more ponds, we’ll contribute to re-establishing our countryside’s diminishing freshwater network and biodiversity’.
