Sand filters are used as a step in the water treatment process of water purification.
There are three main types; rapid (gravity) sand filters, upward flow sand filters and slow sand filters. All three methods are used extensively in the water industry throughout the world. The first two require the use of flocculant chemicals to work effectively while slow sand filters can produce very high quality water free from pathogens, taste and odor without the need for chemical aids Sand filters can, apart from being used in water treatment plates, be used for water purification in singular households as they use materials which are available for most people.

Filter gravel is used as a support media to filter sand and coal in water filters.
For maximum efficiency, filter gravel must possess the necessary attributes of hardness and be rounded rather than angular.
Filter Gravel is a hard, round, predominantly quartz aggregate. The filter gravel, like filter sand, contains hard durable particles with a slow breakdown rate. This helps to prolong filter media life.