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David Pagan Butler - Building Your Own Natural Swimming Pond

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Natural Swimming Pools or Swimming Ponds work with nature to provide hygienic water for swimming. Plants and animals condition the water so there is no need for chlorine or other pesticides. These pools are good for people and wildlife. David built his first Natural Swimming Pool, not because he liked the challenge, but because it was the only way he could afford to have one.

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Over the past five years, David Pagan Butler has built their my own pools and met experts on Natural Swimming Pools, he has re-thought the processes needed to create hygienic swimming water and has come up with a system completely geared to fellow DIY pond builders. He has tried to minimise resources, incorporating reclaimed materials and he has even made filters from reused household objects and domestic plumbing. In addition, his pools use a fraction of the electrical energy most Natural Swimming Pools require to maintain them. All of this is achieved without compromising healthy water. The water was recently tested and shown to be of drinking water quality. And of course, these pools have been designed to benefit wildlife - they are a nature reserve you can swim in! David hopes by showing you how he's done it, you will be inspired to start digging for yourself
How to build a Natural Swimming Pool - with David Pagan Butler.
A one day course designed to equip you with the knowledge to build your own pool.
The day will take you through the whole process and will include practical demonstrations, presentations, tours of existing pools and hands-on sessions. We will meander through the following:
Introduction to Natural Swimming Pools: what they are and how they work.
Water for health and wildlife.
Different building methods and why I chose the method I use.
Siting your pool: considerations and options.
Designing a pool: shape, depth.

Key Tools.
The dig: topsoil and subsoil.
Building: foundations and walls.
Selecting the liner and underliner.
Retaining walls.
Demonstrations of filters, pumps and plumbing.
Maintenance, phases of water clearing, biological population changes.
Your pool as a wildlife rich natural habitat. Pond dipping.
And a compulsary swim - not really, but the option is there for the keen

Contact David

Telephone: 0780 741 8265
David Pagan Butler  - Building Your Own Natural Swimming Pond

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Article printed in Permaculture Magazine, 2010:

DIY Natural Swimming Pond ? David Pagan Butler

Around ten years ago, my partner Alison and I were lucky enough to buy an old derelict barn with two acres of land in Norfolk. The barn is still to be fully renovated but we have been living there in its half-built state for the past four years. My energies have been diverted to a far more exciting building project: three years ago I started making our swimming pond.

I have always thought that it must be possible to build a swimming pool that didn?t use chemicals to keep it clean. One summer, I had seen our water butts either choked with blanket weed or at least go pea-green with other algae. Except for one: the neglected one with couch grass growing in it. Pulling up the floating mat of grass revealed stunningly clear water. I read a book on reed-bed sewerage systems and realised it was basically the same biology as my couch grass water butt algae killer. But instead of reeds taking out the nutrients, it was couch grass. So surely it must also be possible to use other plants to clean a swimming pool? Searching the web to confirm my originality of concept dashed my pretensions of genius. It had all been thought of before. Peter Petrich had been making them, along with others, for twenty years over in Austria and Germany. His company, Biotop, had made hundreds of them.

I couldn?t afford to have a pool built professionally, so building it myself was the only option. At that time, in 2007 there was very little information available for self-build swimming ponds, so it was all a bit of an experiment.

The Natural Swimming Pool (or Swimming Pond ? the same thing) is divided into two equal area zones: one zone for plants, the regeneration zone; and one zone for swimming. The plants have only sand or gravel to grow in so their only chance of getting nutrients is to take it from the water. Then hopefully the algae, like blanket weed, have little left to feed on, so they don?t become a problem. The regeneration zone is separated from the swimming zone by a submerged wall. This is to stop the plants colonising the whole pool.

I decided on a swimming area of 4.5 m by 11.5m, about 2.2m deep, with a shallow 3 m wide regeneration zone all around it. I needed an area roughly 20m by 15m. I chose one corner of the field sheltered by a bramble filled bund. I could also have it aligned north-south, forming a pleasant sun trap at the south side against the bund.

I hired in a man with a digger for a few days and eventually I had a basic shape. My original intention was to build the wall from sandbags filled with sand and clay from the hole. But this was a disaster. When it rained the bags became squidgy, started slithering and slumping until the wall gently collapsed. I tried again, this time filling them with clean sand. These were more stable but the sunlight started to turn the synthetic sandbag material into something no harder than tissue paper. They split and sand trickled out like 25 kilogram egg timers. The wall was punctured with sandbag-sized, empty husks and heaps of sand.

I reluctantly had to start again, this time digging out some foundations for a concrete block wall. I flung the sand from the sandbags into the mixer to make the concrete for the foundation. After a week I built a block wall on the foundation, with solid 100x400x200mm concrete blocks, five courses, to just over one metre high. The void behind the wall was packed with sand and rammed with a tamper (a heavy metal lump on the end of a broom handle), left to settle, and rammed again over a period of weeks. This was to make sure the outward pressure of the water was not going to push the wall over. The land was free draining, containing some clay but mainly stony and sandy. This meant I could lay the liner (with an under-liner) on a layer of building sand laid directly on the pond subsoil floor. If it had been a waterlogged site then the floor would have to be concreted to stop ground water coming up and ?floating? the liner in a completed pond. This concrete box approach is used by some professional installers, as there is very little chance of it going wrong ? but at a cost: a lot of resources and a lot of cash, ?50k or ?60k for a Natural Swimming Pool is not uncommon. Outside the swimming zone the pond floor was formed into a giant basin shape and compacted with a petrol engine driven Wacker plate from a local tool hire company.

My greatest expense was the pond liner. It was also one of the hardest purchasing decisions. There is so much conflicting advice around, a lot of it from manufacturers claiming there is product superior. Pond liners come in various thicknesses and materials. A thicker liner is obviously stronger and more expensive but it is also heavier to manipulate. I opted for 0.75mm EPDM from Flexible Lining Products. Although I think this was more a random choice born from a frustration of indecision. It seems to hold water, so not a bad decision in the end. The liner was going to be buried in shingle contained in a foot deep ditch around the perimeter of the pond, and formed into a curtain drain. This keeps water run-off from the field from entering the pond and introducing nutrients, which would encourage algae. So, taking this into account, I needed a liner, 26m by 20m. It cost ?2,300 ? the most expensive bit of plastic I have ever bought. A fleece under-liner, from the same supplier, was laid in strips over the whole floor and walls of the pond. As part of some film research I was doing, I had just been to see The Swimming Pond Company install a pond in Suffolk and I picked up a vital tip. The fleece under-liner, supplied in a roll, is laid in strips. It needs to be stuck to the next strip to form a blanket over the whole pond area. Strips can be bonded to each other with a blow-lamp. A very quick sweep of the flame along the edge melts a few fibres, so pressing this onto the edge of the next sheet makes them stick together. When the under-liner was complete, the liner was brought next to the pond basin by a friendly farmer with a Teleporter ( a tractor with a large retractable hydraulic arm) and placed onto a small scaffold rig. The roll was suspended on a scaffold pole threaded through the cardboard former the supplier had rolled the liner onto. Now it could be pulled and unrolled rather like a toilet roll. But bigger. The liner was 485kg, and it bent the scaffold pole. Non-the-less, my partner and I, managed to roll it out. A twenty six metre, half-ton snake of liner folded like a concertina. We ?rippled? it along, inch by inch, with a fence post held between us and under the folded liner using a sort of peristaltic motion, rather like the pump in a dialysis machine. We then unfolded the liner and wafted the edges up and down to get air under to help it ?fly? over the whole area. I recommend get as many friends as possible to help. It still would have been hard work even if there were ten of us. It was about this time when I spoke to Michael Littlewood and he sent me his book, Natural Swimming Pools, A Guide for Building. It was great to have some real information at last.

I had made paper models of how the liner should be folded within the shape of my pond. This was very helpful because I knew what shape I was aiming for and where the big folds should come. When the liner was in place and as many creases shuffled out of it as possible, a fleece over liner was laid on top. On top of this sand bags filled with a weak sand cement mix (10 parts sand, 1 cement) were placed immediately above the concrete wall defining the swimming zone. The wall was effectively continued up with more sandbags to a height of around 40 cm. Each row of sandbags pushed back about an inch compared to the row below, making the wall lean outwards against the ballast it has to retain. Flexible drainage pipe was laid around the wall and then buried in shingle. The pipe terminated by emerging through the sandbag wall and into what would be the swimming area. This ultimately helps the water circulate below the roots of the regeneration zone. If necessary, a solar powered pump can be fitted but my pond water, so far, is perfectly happy without any artificial circulation.

I put a geo-textile membrane over the shingle and covered it with many tons of the stony sand that had been excavated from the hole to make the pond. This was all done by hand because machines would damage the various linings. Around the pond I put up a chestnut palling fence. This is for safety. Keeping children or visitors from straying near the pond. It also helps as a wind-break while the newly planted bushes and trees are too small to contribute any resistance. Then it was just a matter of letting the pond fill with rainwater. I pumped it from the water-butts around the house as well, but even with this addition it still took about a year to fill up (over here in East Anglia we don?t get that much rain). But it was well worth waiting for. If I had used tap water the pond could have been be more prone to algae problems. This is because of the phosphorous that is added to mains water, which is effectively a fertiliser. Having said this, commercial installers use mains water, but their ponds then rely on powerful circulation pumps, and filters, including phosphorous filters to help remove the impurities in the water. It was deeply satisfying eventually putting plants into the sand. I had to select them to be ?soft rooted?. I sought guidance from Michael Littlewood?s book ? Natural Swimming Pools. And today, the iris and ranunculus, lilies and curly pondweed are all doing their job wonderfully. Most of the pond and the bank I have just left for wild plants to colonise and the sandy banks are now home to some beautiful tiny native flowers, as well as my friend, couch grass, some of it growing below the water line. And, so far, I have not to needed to artificially pump the water around at all. The plants and animals keep the water crystal clear. Chemical free!

While I was building this pond, I made a film for BBC East Inside Out, on Natural Swimming Ponds and I was privileged enough to meet professional pool builders and Peter Petrich himself. As well as the interview and filming, I had the opportunity to discuss at length some of my non-conventional ideas on Natural Pools. I thought he would dismiss them, but instead, he was very supportive. It was very heartening. Also, I spoke with Michael Littlewood. He, like me, also believed that some commercial companies make their pool far more complicated than they need to be.

Building my own natural swimming pool has been my most rewarding huge experiment. Three years in the making, the eco-system is stabilising and the water is sparkling clear. Just like that couch grassed water butt. I even became fitter than I have ever been with all that digging. And those couple of years of hard work ripple away with every splash of a bathing swallow, and each sight of a kingfisher hunting for water beetles. And of course, there is the joy of swimming in soft rainwater! Your skin fells soft and healthy and your eyes don?t sting with chlorine. One day I think we will look back and wonder how we ever thought is was reasonable to let our children swim in anything other than natural water.


Before building a pond seek planning advice from your local planning authority on whether you need to apply for planning permission. For excellent guides to creating ponds, see

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