Cleaning pool water is a three part process. The first part is carried out in the pool itself through the use of nets, brushes, vacuums and automatic robots and the pool skimmer baskets. The second part is the physical filtering of fine particles from the water. The third and final part is the regulation of the chemical balance of the water through water treatment. The information below deals with the second part - filtration.
Traditionally filtration was always carried out by forcing the pool water through a sand filter, relying on the filtration medium (sand) to trap any particles. As sand has limits on it's ability to do this (it can only filter particles of around 25-30 microns in size), new technologies were sought to increase the efficiency of this part of the water cleaning process.
This led to two new methods of filtering water: firstly using sand filtration equipment but replacing the sand with a volcanic medium called Zeolite or, secondly, using paper cartridge filters.
Paper cartridge filters are able to filter water to around 10-15 microns and are normally used in pairs. In most cases this is an acceptable form of filtration especially as it negates the need for large filters and associated plumbing that is associated with a sand filtration system.
Paper cartridges need cleaning periodically (typically once or twice a week in a heavily used pool during the summer) and will benefit from being replaced once every two to three seasons. Cleaning a cartridge filter is carried out by taking the cartridge out of situ and hosing it down. Particularly heavily soiled cartidges may require them to be steeped in a detergent solution for a number of hours as well. Prices of cartridges vary according to the exact type of cartridge that is specified for your pool but generally range from 84€ to 140€ each.
The housing for paper cartridges can be external to the pool, behind the
pool step ladders or in a "bloc filtrant". Each option has it's benefits and drawbacks but all generally less complicated than sand filtration systems.
The water flow into and out of a sand filter is controlled by multi-way valve to the side or above the filter. This is turned, depending on whether the water should be filtered, cleaned or rinsed. The cleaning & rinsing cycle of a sand filter is usually less than two minutes long.
Zeolite-filled sand filtration systems are for those people who either have to have the very best filtration levels and/or require a less manual & time consuming cleaning method. They are able to filter down to 2-5 microns and still have the benefit of a sand filtration housing. Zeolites also have a longer working life - 5-8 years, with just an annual re-charge necessary. All of our sand filtration based pools are supplied with Zeolite. Replacing your sand with Zeolite will result in cleaner water and pay you back in a very short time through the use of less chemical.
Circulating all of this water, whether cartridge and sand filtered, is a high performance pump. The exact pump that we use would depend on the volume of water in the pool but typically, a 16m³/hr pump is used. More details are available here.