At the latest when the desire for a pool gives way to concrete planning, many pool newbies ask themselves the legitimate question of how and with what to filter the water to ensure consistently good quality. Filter sand, glass particles or rather plastic cotton balls? We explain the common filter systems and provide information about their areas of application, as well as the advantages and disadvantages of the individual working methods.
filter pool
If you want to make the right decision for a functioning filter system, you should first of all know what specific tasks the filter system in the pool actually performs. Overall, the pool water should be freed from organic compounds such as urine and fat, bacteria and germs and also the smallest foreign bodies from dander to dirt particles carried in by the wind. Pathogens and organic compounds are usually eliminated in the water by adding chlorine, active oxygen or bromine. What remains is the filtering of the smallest suspended matter, dust particles, dirt particles, etc. in the pool Since the other components of pool hygiene cannot do this, the filter comes into play here.
How is it filtered?
Regardless of which filter system is used to remove the large number of tiny particles from the pool, the largest possible surface area must first be created. If the contaminated water is passed over this surface, the particles to be removed are deposited on this very surface and can later be permanently removed by backwashing or replacing the filter medium.
Even at first glance at common filter systems, it becomes clear how these basic features of filtering are implemented. Regardless of whether it is filter glass, filter balls or a sand filter system, a medium is always used that strives for an optimal ratio of volume to surface through small grain sizes and thus creates an enormous, technically effective filter surface in the smallest space.
What filter systems are there?
After the theoretical considerations on possible filter systems, let's take a look at which systems have been established for the domestic pool:
The sand filter
The most common form of pool filter is the sand filter system. Filter sand as a medium removes the smallest particles and binds them reliably. The filter sand consists of special quartz sand with a grain size of 0.4 to 0.7 millimeters. The defined grain size thus achieves a standardized filter performance. The sand is placed in a filter housing, in which the supplied water is sucked through the filter layer by negative pressure. In contrast to introduction using overpressure, this method does not create any turbulence in the sand with the release of the already bound particles. The filter sand must be replaced at regular intervals and replaced with new, clean sand. Common material thicknesses in the sand filter system are layer thicknesses from 30 centimeters. Since the filter effect is optimal with a maximum flow rate of 60 meters per hour, the filter surface must be matched to the pool volume and thus the water volume to be filtered.
benefits
- System that has been established and further developed for many years
- High filter performance when using suitable sand grain
- Inexpensive filter material, thus overall low operating costs
disadvantage
- The filter material needs to be changed regularly
- Suitability due to the dependence of filter size on filter volume only for limited pool sizes
notice: The filter sand used can be freed from dirt particles by backwashing, i.e. by pushing water through in the opposite direction. These are fed into the sewage system together with the flushing water. However, the lifespan of the sand can only be extended to a limited extent in this way, but not indefinitely.
Systems with filter glass
A fairly new alternative to the well-known sand filter system is the use of filter glass. Ultimately, this is an identical filter system. Usually even normal sand filter systems are converted to the use of glass particles. The glass particles in the form of fine balls take on the functions that filter sand has previously performed and serve to filter the water in the same way. Compared to sand, glass has a smoother surface, making it more difficult for bacteria and other germs to settle and multiply on it. As a result, systems with filter glass should produce even better water quality. If you believe innumerable field reports on the Internet, after converting from sand to filter glass, there is actually a noticeable improvement in quality with a reduction in turbidity and suspended matter.
benefits
- Less susceptibility to pathogens than filter sand
- Better cleaning properties when backwashing thanks to the smoother surface
- Lower material consumption due to higher cleaning performance and longer service life
disadvantage
- Compared to sand, the price of the filter medium is higher
filter balls
A new development in pool technology is replacing filter sand with filter balls. Filter balls have been known from aquaristics for several decades and are now slowly finding their way into pool technology. They are balls of filter floss made from the plastic polyethylene. The manufacturers promise significantly increased performance when filtering all particles from the pool water compared to filter glass or sand when operated in the same system. The increase in performance is due to a much finer structure and thus a significantly larger surface. In addition, filter balls should be able to filter sunscreen and other dissolved substances from the water in the pool. However, numerous users of such filter balls report only partially satisfactory results. Ultimately, this technology will have to prove itself over time.
benefits
- High filter performance
- Long service life due to washable properties
- Filter performance includes organic compounds
disadvantage
- High costs
- Longevity not yet proven
notice: It is striking that only one type of technical system is required for all of the filter media already mentioned. Both filter glass and filter balls can be used in sand filter systems without any problems, so that the changeover takes place without any significant effort.
filter cartridges
Very small pools usually do without the installation of a complex filter system with a sand filter. Small compact filter systems use so-called filter cartridges, in which different plastic materials with porous properties are used to filter the water in the pool. The cartridges can either be cleaned by hand or replaced with new, clean cartridges.
benefits
- Less effort in operation
- Low system technology required
disadvantage
- High waste accumulation with exchangeable cartridges
- Only suitable for small pools
multi-layer filter
Normal filter systems usually get by with just one filter layer, regardless of the use of filter balls, filter glass or simple sand. For some time now, however, it has been possible to use so-called multi-layer filters. The well-known sand filter can be supplemented with at least a second filter layer, with which unwanted odors can also be removed by using activated carbon or other granules. Since the mode of operation of these additional filter elements corresponds to that of a sand filter, the detailed description is not necessary. The exchange and backwash interval depends on the granulate used.
notice: In most cases, a multi-layer filter serves less to improve the actual water quality than to slightly improve subjective impressions such as smell or taste.