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Navigating Underground Challenges with Precision and Experience

When W.L. Chivers Plumbing was engaged to carry out a below-ground sanitary system upgrade at a residential property in Melbourne’s eastern suburbs, the project initially appeared straightforward. However, as excavation began, our team uncovered a series of unexpected underground obstacles that required a complete re-engineering of the drainage plan, all while maintaining compliance and minimising disruption to the property.

  • Supply and install a new boundary trap in the rear corner of the property.
  • Run a new 100mm PVC sanitary drain diagonally across the yard, including a strategic jump-up beneath a bluestone retaining wall to maintain grade.
  • Replace approximately 41 metres of drain leading to the new connection point.
  • Remove and dispose of concrete along the sideway (14 metres long x 1 metre wide) for access and installation.
  • Adjust the laundry overflow relief gully to align with the new system gradient.
Stage One – Below-Ground Sewer Replacement

Our first phase involved coordinating with Yarra Valley Water contractors to locate the existing sewer connection point, positioned 1.3 metres below ground in the rear easement.

All below-ground works were carried out to AS3500 standards, issued with a VBA compliance certificate, and completed with full site reinstatement using crushed rock for safe pedestrian and vehicle access.

  • Supply and install a new boundary trap in the rear corner of the property.
  • Run a new 100mm PVC sanitary drain diagonally across the yard, including a strategic jump-up beneath a bluestone retaining wall to maintain grade.
  • Replace approximately 41 metres of drain leading to the new connection point.
  • Remove and dispose of concrete along the sideway (14 metres long x 1 metre wide) for access and installation.
  • Adjust the laundry overflow relief gully to align with the new system gradient.
Stage Two – Discovery of Unforeseen Concrete Footing

During excavation, our team encountered a major unforeseen obstruction, a solid concrete footing, approximately 4.5 metres long, 600–800mm wide, and 600mm thick, reinforced with 15mm rebar. This structure was likely part of a former boundary wall or outbuilding footing.

Due to its density and position, removing the footing was not feasible without risking damage to surrounding structures. Instead, we devised a revised drainage strategy that maintained hydraulic efficiency while avoiding the obstruction. This involved adjusting the alignment of the new below-ground system and planning for a suspended sanitary drain to service the internal fixtures.

Stage Three – Suspended Sanitary System Installation (Variation Works)

To ensure long-term reliability, we designed and installed a new suspended 100mm PVC sanitary drain beneath the house.

The suspended drain runs under the subfloor, connecting through the external rear wall into the new below-ground system. We also installed a new overflow relief gully with a compliant garden tap positioned above it for inspection and maintenance access.

This variation included approximately 36 metres of suspended drainwork, seamlessly integrated with the previously installed below-ground section.

This system connects all major internal fixtures, including:

  • Ensuite shower, WC, and basin waste pipes
  • Main bathroom and laundry
  • Kitchen branch line
Transparent Communication and Fair Pricing

Throughout the project, we maintained open communication with the client, providing real-time updates, site photos, and a revised plan that reflected the new conditions on site.

To recognise the unexpected scope change and time lost during excavation, W.L. Chivers Plumbing provided the variation works at a discounted rate, ensuring continuity between both stages while maintaining our high-quality workmanship standards.

  • Full replacement and upgrade of the sanitary drainage system
  • Long-term reliability and maintenance access
  • VBA compliance and Yarra Valley Water coordination
  • Transparent and fair pricing across all stages
Below Ground Sanitary Drain

Below Ground Sanitary Drain

Gas Located

Gas Located