Ag Pipe for Retaining Walls — Agricultural Drainage Pipe for Correct Wall Drainage

Agricultural drainage pipe — commonly called ag pipe — is the primary drainage component installed behind a concrete sleeper retaining wall. Laid at the base of the drainage aggregate layer, ag pipe collects groundwater and surface water that infiltrates behind the wall and channels it to a safe discharge point, preventing hydrostatic pressure buildup that causes walls to lean, crack, and fail.

How Ag Pipe Works in a Retaining Wall

Ag pipe is a perforated flexible pipe wrapped in a geotextile sock that allows water to enter while filtering out fine soil particles. It is laid at the base of the wall on a bed of drainage aggregate (typically 20mm crushed rock), sloped to drain to a discharge point at the end of the wall or through a stormwater connection.

Ag Pipe Installation Guidelines

Lay ag pipe at the base of the wall, sloped at a minimum 1:100 fall to the discharge point
Surround with a minimum 200mm of 20mm drainage aggregate on all sides
Wrap the entire drainage aggregate zone in geotextile fabric to prevent soil migration
Install weep holes through the wall face as a secondary drainage relief
Discharge to a stormwater pit, kerb, or approved drainage point — never onto a neighbouring property

Read our Ag Pipe Installation Guide and Complete Drainage Guide for full detail. See our full Drainage Kits range for complete drainage solutions.

Ag Pipe for Retaining Walls