374 bytes added
, 7 years ago
<poem>
A choking layer of ≥ 100 mm is the recommended method to prevent migration of finer [[filter media]] into an underlying reservoir of [[Reservoir gravel|coarse aggregate]].
Suitable materials include:
;Pea Gravel
:Pea gravel or crushed stone screened between 5 - 15 mm, and washed, free from fines.
;High performance bedding (HPB)
:
</poem>
[[category: materials]]