The sand filter
The sand filter is the biggest-selling private pool filter in France. Its success is due to the fact that it is inexpensive and easy to use.
Pool installers propose several filtration systems which render the water perfectly clean. The most popular filter for private pools is the sand filter. Its manner of functioning couldn't be simpler : the water pumped from the pool is cleaned by passing through different layers of sand which are piled on top of one another in the cartridge of the filter.
When the sand is saturated with dirt, it is cleaned by putting the pump into the "wash" position and by then reversing the flow of water. This filter consists of a cylindrical tank made of reinforced polyester, or steel covered with polyester, or epoxy. It is filled with sand (silica). Each filter is linked to a gauge which verifies the outflow of filtration, and a multi-functional gate (wash, empty, filter, rince and stop). When the sand is saturated with dirt, the pressure gauge rises and this indicates that it needs to be washed. In normal use, the pump should be washed once a week.
The size of the sand filter you require depends on the amount of water to be filtered and on the power of the pump. Several different models are available. Some are 'slow', other 'fast' and others in between. Some filters have a double flow system or are multilayered. The speed of filtration varies from 9 to 30 cubic metres per hour, depending on the model. Filtration with a sand filter isn't very fine, but it is good enough to keep the water clean (between 20 and 30 microns). Filtration can be improved by adding a thickening agent to the water, but doing so means cleaning the filter more often.
Generally speaking, the sand filter is good value for money for normal pools, even if more efficient systems are available. The sand filter is inexpensive and it is suitable to all types of water -soft, hard, salty or not. It is therfore suited to all conditions and does the job asked of it. The disadvantage of this filter is that it consumes a lot of water, as the sand has to be thoroughly cleaned every week. Another disadvantage is its bulky size - it is not very pretty to look at beside the pool !