![\"Finished](\"http:\/\/www.insitucon.co.za\/wp-content\/uploads\/2011\/02\/IMAG0399.jpg\" "\\"Finished")
<\/a>Finished pool<\/p><\/div>\n
This is the third pool we have “self built” and we used much of what we had learnt with the first two in this one. One major difference this time is that we decided that we wanted to build a natural swimming pool. What is a natural swimming pool you might ask? Well my definition is a swimming pool that doesn’t require the addition of any chemicals, relying on natural processes to keep the water clean and clear. If correctly designed, the idea is that pool becomes an extension of the garden and becomes part of your garden\u2019s ecology.<\/p>\n
The basic principle of how a natural swimming pool works is, in order to keep the water clear, you need to deprive the algae which is always present in the water of nutrients. This is achieved by the large number of plants and large areas of gravel that the water flows through. The plants and the bacteria that colonise their roots and stones, compete with the algae keeping the nitrate and phosphate levels low. Low levels of these nutrients\u00a0means\u00a0the algae simply cannot bloom and the water stays clear.<\/p>\n
The idea of natural pools is not\u00a0particularly\u00a0new and they do seem to be gaining popularity, however\u00a0getting\u00a0reliable and useful information on how to tackle a natural swimming pool turned out to be quite a challenge. Whilst there are quite a number of sites which showcase the projects completed by pool contractors, as well as companies selling bio-filters and related equipment. We found they were very skimpy on details. Some forums do exist which did offer some advice, but generally these were more\u00a0orientated\u00a0towards Koi ponds.<\/p>\n
This lack of\u00a0available\u00a0info is something which I am sure will change as natural\u00a0swimming\u00a0pools become more commonplace, especially here in South Africa, although I suspect most experts will probably keep the info close to their chests. A book that did help a bit was “Natural Swimming Pools: A Guide to Building by\u00a0Michael Littlewood”, however I found it did lack much of the nitty-gritty on how to actually build a pool. So after much reading both along and between the lines here are the basic principles for what I believe will make a\u00a0successful\u00a0natural swimming pool:<\/p>\n
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- The planted area needs to be about the same surface area as the swimming area (ie. 50 \/ 50)<\/li>\n
- Swimming area needs to be as deep as possible, at least 1.5m (increases volume of water without increasing area exposed to sunlight)<\/li>\n
- The water needs to circulate slowly but constantly through the system.<\/li>\n
- Total size should be as big as possible (Littlewood refers to a minimum area of 50 sq meters – we broke this rule and opted for an area of 25 sq meters due to space constraints)<\/li>\n
- Water needs to be well oxygenated (plants and\/or water action)<\/li>\n
- You need to provide maximum surface area for beneficial bacteria to colonise ie. roots and gravel beds.<\/li>\n<\/ul>\n
Because our garden was not big enough to accommodate a large organically shaped pool and also there is a significant level difference between the floor\/deck and garden level, we decided to opt for a more contemporary design. \u00a0Here is the final Sketchup drawing showing the planned shape prior to me drawing up the final details. The physical sizes are as follows:<\/p>\n
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- Main swimming area : 2.4 m x 4.4 m – depth 2.4m with a continous step along the deck side.<\/li>\n
- Intermediate pond: 1 m x 2.2 m – depth 1.2 m<\/li>\n
- Lower pond : 0.8 m wide x +-10 m long – depth 0.6 m but varies from 0.1 m to about 0.4 m with the gravel inside.<\/li>\n
- Total volume 25 500\u00a0litres<\/li>\n<\/ul>\n
![\"Sketchup\"](\"http:\/\/www.insitucon.co.za\/wp-content\/uploads\/2011\/02\/Capture-300x165.jpg\" "\\"Pool")
<\/a>Pool Concept<\/p><\/div>\n
Because\u00a0we wanted the swimming area to be close to deck level we decided to terrace the pool with the planted sections stepping down to the garden level. This way there was some\u00a0continuity between the deck \/ pool level and the grass lower down. One thing we did pick up from other designs was that the water is almost always flows from under the planted area up and towards the deeper swimming area. In our design this wasn’t really possible, but since we\u00a0couldn’t\u00a0find\u00a0any logical\u00a0reason way it would make a difference\u00a0reversing the flow, we decided to try it out in reverse.<\/p>\n
![\"Digging](\"http:\/\/www.insitucon.co.za\/wp-content\/uploads\/2011\/02\/IMG_3930-300x225.jpg\" "\\"The")
<\/a>The Digging Starts<\/p><\/div>\n
In terms of physical construction we decided on using standard 190mm wide\u00a0masonry\u00a0blocks, reinforced with reinforcing steel and concrete in-fill. The reason for this is we wanted to have narrow as possible walls, and this was the only way I could think of\u00a0achieving\u00a0this without going the shuttered reinforced concrete route. To waterproof the structure a glass-fibre reinforced resin system again proved to be a cost-effective solution. Prior to fibre glassing the block-work was simply plastered to the desired shape and detail and allowed to harden.<\/p>\n
![\"First](\"http:\/\/www.insitucon.co.za\/wp-content\/uploads\/2011\/02\/IMAG0061-300x179.jpg\" "\\"First")
<\/a>First course of blocks<\/p><\/div>\n
![\"Block](\"http:\/\/www.insitucon.co.za\/wp-content\/uploads\/2011\/02\/IMAG0118-300x179.jpg\" "\\"Block")
<\/a>Block work complete<\/p><\/div>\n
A large part of any natural swimming pool is obviously the water plants and we were\u00a0 very fortunate that my lovely Mum was easily persuaded to start collecting and cultivating plants. I think she even started collecting before we had started digging the pool. She has very green fingers and very soon had quite a collection of plants happily growing in some temporary containers. Apologies to the neighbours who had to put up with all the mosquitoes who obviously loved the still, stagnant water. It\u2019s interesting to note that there are no mosquitoes in the swimming pool, which I am sure is mainly due to the running water and our collection of eight hungry mosquito fish.<\/p>\n