The filtration process

A swimming pool must be filtered to remove insoluble particles and produce clear water.

Filtration is the physical removal of neutralised contaminants (chemicals, debris and other waste), together with the insoluble particles from the water. Clear water is desirable not only for aesthetic reasons, but for hygiene and safety.

Daily filtration cycles will vary but should be between 6 to 12 hours depending on time of year and the size and type of the system installed. It is important that at least one “turnover” is achieved - that is, as a minimum, the equivalent volume of the pool or spa is filtered each 8 hours. Filtration cycle times are best split over 2 to 3 sessions per day. You may need to increase the filtration cycle times during periods where there is a higher bather load.

The filtration system

While filtration systems may differ regarding their type, they will all have the following basic features:

  • a skimmer box which allows water to enter and capture surface debris via the skimmer’s weir. A weir is the front flap located on the front of your skimmer.
  • an initial leaf basket in the skimmer to trap leaves and large debris, before the water is sucked through to the pump and filter.
  • a secondary basket situated within the pump, commonly referred to as a hair and lint
  • a circulating
  • a filter which physically removes solids from the
  • Pipework through which the water is circulated throughout the pool or spa.

Refer to our page on equipment setup for diagrams of the filtration system.

Types of filters

All filtration relies on removing solid matter from the water as it is pumped through the filter. The quality of filtration depends on the size of the filter media. The finer the media, the higher the purity of water obtained. There are three common types of filters:

  • Media – sand, glass or zeolite
  • Diatomaceous Earth
  • Cartridge

The finer the filter media, the faster the increase in pressure across the filter bed, and the more frequent the need for backwashing or filter replacement.

All of these filter types have high flow characteristics and are highly efficient.  Regular cleaning is required to remove entrapped solids, reduce pressure within the filter tank and improve water flow for filtration and vacuuming, chlorination and circulation within the pool.

Most filters will have an indication on the filter’s pressure gauge when cleaning is necessary. Cleaning methods will depend upon the filter type. Media filters can be “backwashed”, which is to reverse the flow of water through the filter tank valve and flush debris to waste. Cartridge filters require removal of the cartridge so that it can be hosed down and then soaked in cartridge cleaning fluid.

It is recommended to follow the manufacturer’s cleaning directions. In addition to regular cleaning, periodic service of the filter is recommended to remove any build-up of grease and scale. This can be arranged through your local SPASA Service Technician.

Discharging water

Discharging wastewater during a backwash cycle or hosing down a cartridge filter is an important part of filter maintenance; however, it is important to note that wastewater being discharged must not be disposed of via any storm water system or allowed to simply run off onto adjoining land. You may need to make enquiries with your local council or water provider to see what is permissible in your state or territory.

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