Sand (silica) in its different forms (sand, silex, gravel) is the oldest natural available granular filtration media. Even today, the use of sand remains popular for the treatment of municipal water in very big open gravity filters, in swimming pool filters and in pressurized filters for the treatment of ground water.

In a lot of groundwater applications the use of sand has been replaced with other granular filtration offering more benefits (faster flow rate, better quality of filtrate, lower in weight, etc.)

Sand is present in nature all over the world, washed and sieved. It exists in different grades that vary from one supplier to another. It is used for the removal of suspended solids, but can also be used to filter of oxidized iron or manganese.

A pressurized sand filter always contains different layers of sand, going from relatively fine sand on top to coarse gravel as a support layer. In between the use of 2 more particle sizes is common.