Design (Natural Swimming Pool)

Ever since moving to Phillipskop in 2014, we have wanted to build a swimming pool. However, it was important for us that it fitted in with the habitat and landscape that we are conserving here. A natural swimming pool was therefore the obvious route to go but such projects cannot be achieved overnight. Here we want to share with you some of the planning, concepts and challenges we faced in achieving this goal. No two situations are ever alike, but hopefully this will inspire others who are thinking along a similar idea.

The first challenge in our design was to decide on a size of the swimming pool and filtration area. The simple principle in a natural swimming pool is that there needs to be an equal size of planted filtration area to swimming area. Below the self-catering chalets was an area that had been dug out to create a dam in the distant past but had never been completed. This was fortunate for us in that we did not need to remove any more natural vegetation than had already been done historically. However, we were never going to use the whole area as a swimming pool as it would have require vast quantities of water to keep filled especially during the hot summer months. We therefore had the freedom to build as large a pool and filtration area as necessary but to balance the size of the pool with the eventual cost of the whole project and the need to provide sufficient water. In terms of cost, our aim was to keep the final budget below R1,000,000 (±$70,000 at the time).

We originally toyed with the idea of constructing both the filtration and swimming areas out of a unified concrete structure, but this would have meant that around half our construction costs would have been spent on a non-swimming area. We were also warned about the challenge it might be to bring ready-mixed concrete up the hill onto the reserve (in the end this did not prove to be the case, but we designed on the basis of minimising concrete). We therefore settled on a footprint of about 12 x 6m for the swimming pool. Then adjacent to this we proposed a sealed pond to act as the filtration area. We chose to shape our pool so that it narrowed at the deep end, in order to maximise length whilst slightly reducing area (and therefore cost) and enable the filtration pond to wrap around two sides in a natural-looking way. The main cost in the size of the pond would be the sealing clay – cheap compared with a concrete structure. We were therefore able to be generous and eventually ended up with a filtration pond almost three times the size of the swimming pool. The reason for this generosity was two-fold: increasing plant cover to provide better cleaning of the water and increasing the volume of water available so that the pool needed refilling less often.

The swimming pool has a depth of 1.8m at the deep end, sloping up halfway to the 1m deep shallow end. There are steps at the shallow end across the width of the pool so that very young children and their parents can enjoy even shallower water. There is also a ramp here, which enables frogs and other animals to climb out and not get stuck in the pool. (Despite what many people would think, frogs can actually “drown” in water if they cannot get enough oxygen. It depends a bit on the species, some toads are particularly susceptible, while others such as platannas, can stay submerged almost indefinitely.) The water circulates via a pump in a separate chamber, drawing water in from the filtration pond and pumping it out into the shallow end of the pool. There is then an overflow at the deep end (which also enables frogs to escape), down a metal spill, back into the filtration pond. The filtration pond descends to the same level as the deep end, but as the water level is lower it only reaches 1.5m at its deepest point. Our builder recommended the decking around two sides of the pool, which has proved an excellent feature, enabling swimmers to access the pool from all sides.