How pool water filtrations works



Most modern swimming pools are equipped with sand or cartridge filters manufactured by Hayward or one of the other manufacturers like RTM or Magic and supplied by Certikin or Procopi.

Swimming pool pumps are at the heart of the pool filtration system and are also manufactured by Hayward and other companies like Pentair or Eurostar

This page of the website explains how the pool water filtration system works and how the different elements are designed.

Water Source and Changes

Swimming pools must always be filled from the public water supply where are the quality and cleanliness is guaranteed.

Never take the risk of filling the swimming pool water from the well just to save a few euros or pounds. Even if water does not cause a health problem the trace minerals are almost certain to be beyond the limits specified by the manufacturer of the PVC vinyl pool liner

The pool water must be regularly diluted by additonal water to avoid the long term build up of dangerous pollutants. If a pool is backwashed once a week the dilution will be satisfactory.

Water Clarity and Transparency

The first principle is that if the water looks clear and transparent it will be safe to bathe in - and if not - it is probably not safe!


Turbidity is the name given to the pool water pollutants that are in suspension in the water. They can be large particles or very fine and mineral or organic.

They get into the pool water from being airborne, water borne by rainwater or from animals and people,

Covers are used primarily to stop airborne pollutants and the landscaping design should stop rainwater from carrying debris into the swimming pool.

The pollutants carried in by bathers have to be removed by the pool water filtration system.

The Identification of Turbidity

Generally if you cannot see the main drain in the middle of the bottom of a private pool, then the water is probably unsafe to swim in.

Water Circulation

If the pool water filtration system has been operating satisfactorily and the filtration system needs to be turned off for any reason than the water should be safe for about a day (depending on the water temperature) - but to be on the safe always run the filtration system for a couple of hours before using the pool. And make sure that the chlorine levels are satisfactory.

When starting up a filtration system from scratch any turbidity should be cleared within about 72 hours. If it is not their is probably something wrong with the filtration system.