Pipe Material Selection
How material choice interacts with strength, durability and constructability.
Material selection fixes the pipe's stiffness, its chemical durability, its joint performance and much of its installed cost. The choice is constrained first by what the authority permits in that catchment, then by diameter range, cover, groundwater, bedding and loading.
Gravity sewer materials in Australian practice include PVC-U, polyethylene, reinforced concrete, glass-reinforced plastic and, in legacy assets, vitrified clay and fibre cement. Each has a different design basis: flexible pipes rely on soil support and are checked for deflection, rigid pipes are checked for load and crack control.
Reference table
| Material | Typical role | Primary design basis |
|---|---|---|
| PVC-U | Small to medium diameter gravity sewers | Flexible: stiffness class, deflection and bedding |
| Polyethylene | Where flexibility, length or relocation is valuable | Flexible: deflection, ring stiffness, jointing |
| Reinforced concrete | Large diameter and heavy loading | Rigid: load class, bedding factor, crack control |
| Glass-reinforced plastic | Large diameter, corrosive environments | Flexible: stiffness and deflection |
Key design considerations
- Materials permitted by the authority's supplement and asset standards, including for property connections.
- Strength or stiffness class appropriate to cover, loading and bedding.
- Chemical resistance, especially to hydrogen sulfide and sulfate-bearing ground.
- Joint type and its tolerance to movement and groundwater.
- Abrasion resistance where velocities or grit loads are high.
- Availability in the required diameters, and the contractor's familiarity.
- Whole-of-life cost, including maintenance and replacement difficulty.
Design checks
- Material permitted by the current authority specification.
- Product compliance to the nominated pipe standard.
- Structural class adequate for the deepest and shallowest cover on the alignment.
Standards and authority references
- Authority material specification and asset standards
- AS/NZS 2566.1 Buried flexible pipelines — Structural design
- AS/NZS 3725 Design for installation of buried concrete pipes
- Product standards for PVC-U, polyethylene, concrete and GRP pipes as nominated by the authority
Confirm the current edition, amendment and any local supplement before applying any of the above.
Limitations and assumptions
- Product standard numbers and classes are not reproduced here; confirm against the current edition and the authority's list.
- Legacy materials in existing assets may not be permitted for new work.
This reference is general engineering information. Confirm requirements against WSA 02, the current Australian Standards and the local water authority's supplement before use in design, and obtain project-specific advice for the conditions at hand.