Filter aggregates generally consist of sand, gravel, or crushed rock. Manufactured aggregates are also occasionally used and these often include blast furnace slags.

Although filter materials for water and effluent treatment works are often used in relatively small quantities, the high quality of aggregate normally required is not always readily available from commercial production processing, which may be designed to yield a satisfactory general-purpose aggregate at least cost. On the other hand, drainage layers in major civil engineering works, such as embankment dams, are usually designed to make the best use of the available natural materials with the minimum of processing.