Sewer Encasements: Encasing a pipe in concrete to provide strength and protection
When building over the zone of influence of an existing sewer, a concrete encasement is a very common requirement of the Section 73 Compliance Certificate.
Encasing a pipe in concrete will provide strength to the existing asset and will provide additional protection to the pipe from unexpected external load and movement, reducing the risk of damage and consequently the need for repairs.
A lot of the existing sewer mains and pipelines around Sydney are made of clay or cast iron, and it is generally recommended that these or any deteriorating pipes, be removed and replaced with PVC pipe. The PVC pipe is then surrounded in concrete to create the sewer encasement.
Permanent or temporary building works that may adversely impact the sewer main and usually require an encasement include residential, commercial and industrial works such as:
- Swimming pools and water tanks
- Carports, verandahs, pergolas, and sheds
- Decks and retaining walls
- Driveways and pavement areas
- Planting trees and landscaping
- Demolition and excavation
- Roads and civil infrastructure
Sewer Encasement Process
Before you can receive a Section 73 Compliance Certificate, you will need to adhere to the Sydney Water requirements, and these may include the need for a sewer encasement. All Line Plumbing will usually liaise with a Water Servicing Coordinator (WSC) or engineer and install an approved design. The most common sewer encasement process is:
- Excavate the pipe
- Renew or replace the pipe with PVC
- Secure and support the underside of the pipe using concrete bags or blocks
- Secure and strap down the top of the pipe with timbers so the pipe does not float while installing the concrete
- Inspection and approval by the WSC or engineer
- Pour concrete per the design of the WSC or engineer
- Backfill and compact trench as required