Cartridge filters: a little-known product
The cartridge filter is a piece of pool equipment that is not well known, to the extent that less than 20% of pools in France feature one. The cartridge filter's image has been significantly tainted by the basic products generally sold with above ground pools.
However it has undeniable advantages in relation to granular media filters in terms of efficiency and filtration quality. What’s more, it requires little maintenance and enables real savings to be made on water, electricity and treatment products, which are necessary and even indispensable conditions for more virtuous pools.
Principle of operation
The cartridge filter functions in a radically different way to granular media filters. It works via surface filtration and not via deep filtration like the sand filter. It is able to trap small or large impurities without needing to be filled with sand of different grain sizes. Flocculant, which is generally aluminium salt-based, no longer needs to be added either to capture the small pollutants. The result is a filtration fineness of 20 to 25 microns compared to 40 to 50 microns for sand.
Another important difference is that the filtration quality of the cartridge filter is less dependent on the water speed. It filters with the same efficiency whether it operates slowly or quickly, in contrast to the sand filter which needs a slow filtration speed to be efficient and to leave time for its filtering media to capture more impurities.
Another of its characteristics is that each element of this filter does not require backwashing. Moreover, the more they become clogged, the more efficient they are . In fact, the debris are automatically distributed over the whole surface, with the water seeking the quickest route.
By ensuring that the filter is chosen according to the necessary flow and its retention capacity (with an oversized or multi-cartridge filter for pools particularly exposed to dirt and debris), each element simply needs to be cleaned once a season as indicated on the manometer. Cartridges that are well-maintained and de-scaled every year can last four to six years, which is almost the same lifespan as sand filter media, and they are infinitely easier to transport, install and discard than 150 kg of sand, for example.
How is the efficiency of a pool filter measured?
The efficiency of a pool filter is determined by its filtration fineness and its retention capacity. To increase this filtering power, simply extend its filtering surface. In the case of a granular media filter, the filter diameter and therefore the media volume must be increased, which increases the pressure drop and requires a pump that is sufficiently powerful for backwashing. This is why a variable speed pump is beneficial for this type of filter.
The cartridge filter: a tool for the virtuous pool
The cartridge filter is the ideal product for more virtuous operation of pools.
- Less water discharge from backwashing i.e up to 6,000 litres of water (6m3) in relation to a classic sand filter. This is a key aspect in an era in which environmental regulations are being tightened up and more municipalities are banning wastewater discharge into nature ;
- Cleaning once per season with a 4 element filter ;
- Reduced pressure drops compared to a sand filter ;
- More appropriate chemical treatment thanks to its filtration capacity and no flocculation and backwashing ; (reduced salt loss for electrolysers) ;
- Small dimensions for installation in the technical room and possibilities to extend its filtering capacity. What’s more, a cartridge filter is much lighter than a full sand filter and its production and transport also emit less CO2.
The cartridge filter is therefore one of the indispensable pieces of equipment for a virtuous pool: it improves operation and enables consumption and the ecological impact in general to be reduced.