Grade Selection

Grade  1 or 1N  is generally selected for pressure filter applications.

Grade  2 or 2N  is used in both gravity and pressure filters.

Grade  3 has a growing application in gravity filters for the tertiary treatment sewage.

Grades  4 - 7 are generally used as support layers.

N Denotes non-standard sizing and these grades are only manufactured to order.  Other non -standard sizes are also available on the same basis.