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How does a pool work?

For many of us, the workings of a swimming pool are a complete mystery. However, it is essential that we understand the basic principles and how the various items of equipment interact. Follow the water and, through the diagram below, discover what you have always wanted to ask about swimming pools but have never dared to…



Key to the diagram:

  • 1 -Spa (with nozzles): optional
  • 8 - Water treatment system (here: electrolyser)
  • 2 - Skimmers (2)
  • 9 - Lights (2)
  • 3 - Level control
  • 10 - Light connection box
  • 4 - Main drain
  • 11 - Suction inlet
  • 5 - Pump
  • 12 - Automatic pool cleaner
  • 6 - Filter
  • 13 - Booster pump (for pressure automatic cleaner)
  • 7 - Heat pump
  • 14 - Electrics box



1) Water collection

Skimmers collect and skim water on the surface (2/3rds) by propelling the water towards the filters and screening out the largest debris in their strainer basket while the main drain collects the colder water from the bottom (1/3rd) for improved mixing. This enables us to not only produce evenly heated water but also its uniform chemical treatment because the treatment products are evenly distributed throughout the pool.

2) Suction and filtration

The pump is also fitted with a strainer basket to trap foreign bodies and draws up water that it sends to the filter which is the key component of this installation. The filter screens out impurities in order to guarantee clean water, a crucial consideration for pleasant bathing and for the system’s longevity. Warning: this pump/filter pairing must be perfectly matched as the pump output must never exceed the capacity of the filter. There are different types of filter but all require regular maintenance.

3) Heating

After it leaves the filter, water can be heated using a variety of systems: electric heater, solar panels and, in this case, a heat pump

4) Water treatment

Water treatment is the final step water undergoes. There are several more or less automated processes designed to achieve water that is constantly perfectly healthy and balanced. In this case, it is an electrolyser. We cannot stress enough the importance of water treatment. Here again, opting for a low cost system can result in considerable inconvenience because the water’s balance is a delicate one and requires constant monitoring.
Warning: all this equipment is interlinked by pipes; if they are not properly dimensioned, then the system will not work. So we need to establish the correct ratio. Pool size is used to calculate the theoretical output that must be produced by the pump and the filter. Accordingly, we calculate pump power, filter capacity and pipe diameters bearing in mind that the water in the pool should be renewed 3 to 6 times in 24 hours.

5) Maintenance and lighting

The cleaner socket is used to adapt different types of automated pool cleaners used for swimming pool maintenance.
Finally, lights allow the pool to be used at night and enhance its appearance. There are two available technologies: the classic 300 Watt halogen light or the colour LED which is becoming increasingly more common.

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