Pool Water Treatment System – An Overview

Pool water treatment system.

For the purposes of this article, we can consider the Pool Water Treatment System as everything the pool water flows through as it travels from the pool to the plant room and back to the pool again. Substances for disinfectionpH correction and coagulation are injected into the pipework along the way.


The circulation pumps are the ‘heart’ of the system. They are designed to continuously pump water around the system at a pre-determined rate called the flow rate. In larger installations, there are usually several pumps working at the same time, with additional pump(s) on standby. In smaller installations, there may only be one single pump.


Vessels containing a bed of filter media (usually sand). The pool water gets pushed through the gaps between the grains of sand, where much of the pollution is trapped.

Filtration is an essential part of swimming pool water treatment and its importance has been emphasised in recent years due to several outbreaks of cryptosporidiosis, because this organism is not killed by the disinfectant in the pool water and therefore must be removed by filtration in order to prevent bathers becoming infected by it.

Filtration is a fairly simple process; water leaves the pool via the deep end outlets and the surface water draw-off system (deck-level, skimmer baskets, overflow channels etc.). It is piped to the plant room and gets directed into the top of the filter (or several filters in large pools), passes through the filter media (usually sand) where all the contaminants and pollution are trapped and the pool water comes out of the bottom and continues through the remaining components of the pool plant system.


The heat exchanger is usually the final component that the pool water is circulated through before it is returned to the swimming pool.

Water is heated by the boiler (or other heat source) and circulated through copper pipes around the building. This is called the domestic hot water (DHW) and supplies hot water to the hot water taps and showers etc. It also gets piped to the heat exchanger.

Swimming pool water also gets directed to the heat exchanger and flows through the chamber containing the coil (if a coil heat exchanger is installed, or in between the hot plates (if a plate heat exchanger is installed).

The pool water never actually mixes with the domestic water, but picks up the heat it requires from the coil or the plates before being circulated back to the pool. The temperature is controlled via a motorised valve fitted to the domestic how water flow pipe, which is connected to a thermostat and automatically opens and closed the motorised valve depending on whether more or less heat is required.