Sand filters are a popular choice for swimming pools because they are easy to install, reliable, simple to maintain, and cost-effective. There are three main types of sand filters: steel, thermo-plastic, and fibreglass. The latter two, which are non-corrosive and easy to service, are most commonly found in pools.
However, each type has its own strengths and may be better suited for certain conditions. The filtration medium in sand filters is usually a particular grade of very fine silica sand, which should be purchased through a swimming pool specialist. As dirt builds up in the sand, it gradually increases the back pressure, which can be monitored by a pressure gauge to determine the filter's effectiveness and when the medium needs to be cleaned.
Cleaning or backwashing the sand is a simple process that involves switching off the pump, altering the position of a rotary or multiport valve, and turning the pump back on to reverse the water flow. This expands and agitates the sand bed, allowing the water to carry dirt particles away to a waste outlet. Depending on the frequency of pool use, this process may only take a few minutes and may only need to be done once a week in the peak season.