Installing Drainage Around Sandstone Retaining Walls
Our team attended a property in Blaxland to install subsoil drainage across two levels of the site.
The property required drainage along several sandstone retaining walls, including the front and side boundaries on the upper level and the rear retaining wall on the lower level.
Rather than installing one continuous drainage line, the project involved two separate collection arrangements, each with its own 300mm drainage pit and connecting pipework.
The upper level also required a herringbone drainage layout and new PVC pipework through the subfloor, while the lower level involved drilling through a sandstone retaining wall to accommodate the discharge pipe.
Excavating Along the Upper Sandstone Retaining Wall
Work began with excavation along the sandstone retaining wall at the front of the property and the right-hand side boundary.
These trenches provided space for the new subsoil collection pipework.
A core hole was also drilled through the external wall to create an opening into the subfloor area, where additional drainage pipework needed to be installed.
Installing the Upper-Level Herringbone Drainage System
The upper drainage system was installed in a herringbone formation, with multiple collection lines feeding into the drainage network.
This arrangement allowed the pipework to collect water across the designated area rather than relying on a single straight drainage run.
A new 300mm drainage pit was installed in the front yard to form part of the collection system.
The trenches were lined with geotextile fabric and builders plastic, with 10mm aggregate placed around the subsoil drainage pipework.
The aggregate provides space for water to move towards the drainage pipes, while the geotextile helps limit surrounding soil entering the drainage material.
Approximately 50–100mm was left at the top of the upper trenches so the property owner could finish the surface with decorative pebbles or rocks.
Connecting the New Drainage Through the Subfloor
The upper-level installation also required new 100mm PVC drainage pipework through the subfloor.
The pipework was routed through the wall opening and connected to the property's existing terracotta drainage.
This provided a connection between the newly installed subsoil drainage and the existing drainage infrastructure.
Installing Subsoil Drainage Along the Lower Retaining Wall
With the upper-level drainage installed, work continued along the rear left-hand sandstone retaining wall.
A second subsoil collection system was installed along the wall, extending towards the rear corner of the property.
This section included another 300mm drainage pit and drainage pipework positioned along the designated collection route.
The lower-level trenches were backfilled with soil and aggregate as specified.
Drilling Through the Sandstone Wall for the Drainage Outlet
One of the more involved parts of the lower-level installation was creating an outlet through the existing sandstone retaining wall.
A core hole was drilled through the wall to accommodate new 100mm PVC discharge pipework.
The pipework was routed through the opening towards the neighbouring land at the rear, as specified in the installation scope.
This established the planned discharge route for the lower drainage system.
Testing and Completing Both Drainage Systems
Once the upper and lower subsoil drainage systems were installed, the completed works were tested and commissioned.
Installation waste was removed and the work areas cleaned.
The completed project provided drainage infrastructure across two separate levels of the Blaxland property, including:
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Herringbone subsoil drainage along the upper retaining wall and side boundary.
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Two new 300mm drainage pits.
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New 100mm PVC pipework through the subfloor.
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A connection to the existing terracotta drainage.
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Lower-level subsoil drainage along the rear sandstone retaining wall.
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A new drainage outlet through the rear retaining wall.
Together, these installations provide dedicated collection pathways for water moving through the ground around the property's retaining walls.
Related Subsoil & Stormwater Drainage Services
Pure Plumbing Professionals provides Stormwater Drainage, Subsoil Drainage, CCTV Pipe Inspections and Plumbing Maintenance throughout Blaxland and surrounding Sydney suburbs.
Related work can include retaining wall drainage, subfloor drainage, drainage pit installation, underground PVC pipework and stormwater drainage repairs.
