Designing a pool is not as simple as it sounds. Better to follow a number of rules. Philippe Asseray, landscape gardener and specialist journalist, reveals the keys to a successful pool.
Are there several kinds of pools?
Yes. You have the choice between an above-ground basin, the least restrictive, which can be installed in a small space and which is emptied during the winter, and the buried basin. The buried basin is of two types: with a liner at the bottom (like for a swimming pool) and it looks like a natural pond, or else the masonry basin with a stone or brick ledge.
What questions should you ask yourself before you start making your pool?
First, are we ready to embark on the adventure? Because you should know that maintaining a pool is restrictive. Once you are sure of your decision, choose the ideal location, sunny and located in the lowest part of the garden if it is sloping. Finally, we must think about the dimensions we want to give it. The larger a pool, the easier it will be to manage and maintain afterwards because the water rots less and filters itself. By "large pool", I mean at least 10 m².
How do you make your pool?
We dig then, on the smoothed bottom, we put a garden felt to avoid that the stones and the roots do not come to pierce the liner. It is an essential step! Then we put the liner, which is a kind of black plastic sheet. I recommend the EPDM tarpaulins which are thicker and more resistant. We fill three-quarters with water. The weight of the water then places the tarpaulin at the bottom. Then we cut the tarp all around the basin, leaving 30 or 40 cm beyond it that we will hide with stones, earth, gravel, pebbles or whatever you want. Then check that the pool is level and plan an "overflow", useful in case of heavy rain, ensuring that the water can overflow to a corner of the garden that does not interfere. We can then finish filling it.
When are the plants installed?
We wait 3 or 4 weeks for the water to "settle" before installing the plants. The ideal is to put them in "baskets". These are sort of openwork plastic boxes, which are filled with soil and compost before placing the aquatic plant and stones to prevent the earth from rising. These baskets are then immersed in the bottom of the basin. This system makes it easy to remove plants when they become too large and need to be divided, or if the winter is very harsh and you want to remove them.
Which plants to choose?
There are a lot of aquatic plants. A rule of thumb is to always start by putting so-called "oxygenating" plants, such as waterweed, milfoil or water pessae. They are not the prettiest but they are very useful to avoid the formation of algae. Then treat yourself with the plants you like. Please note, some of them have immersion depth constraints. Ask the question carefully when you buy them.
When can we put fish?
Wait a month after planting to put the fish. Thus, the plants will be well rooted and the fish will not be able to uproot them.
Should we install a filtration system?
The smaller the basin, the more essential a filtration system is. The ideal is to install an external filter to the basin, which one will hide with shrubs. An electrical connection must be provided when the pool is designed, which represents additional work. One pipe sucks the water and another discharges the filtered water into the basin. You can create a small jet of water or a small waterfall so that it looks prettier than a simple hose. However, a pool of more than 10 m² can self-regulate. The larger the volume of water, the more naturally the water oxygenates and the less the water rots.
To know more :
Read "Basins tout simples" by Philippe Asseray, Larousse, Les Petits Truffaut collection.