Where Are Articulation Joints Needed in Plumbing?

In Australian plumbing systems, particularly underground sanitary and stormwater drainage, articulation joints play a crucial role in keeping pipes watertight and functional over the long term. Their use is not optional—they are required by the National Construction Code (NCC – Volume 3, Plumbing Code of Australia) and AS/NZS 3500.2: Sanitary Plumbing and Drainage, especially on sites where soil movement is expected.

But where exactly are articulation joints needed?

1. At the Connection to Buildings

Whenever pipes pass through or exit a building foundation, slab, or retaining wall, articulation joints must be installed. These locations are especially vulnerable to differential movement between the structure and the surrounding soil. The joint absorbs this movement and prevents cracking of the pipe.

2. In Reactive Soil Sites

If a site classification report (AS 2870 – Residential Slabs and Footings) identifies reactive clay soils (Class M, H, E or P), articulation joints are mandatory. These soils shrink and swell significantly with moisture changes, which can place major stress on rigid pipework.

• Class H1/H2 (highly reactive clay) – joints are typically required at closer spacing.

• Class E (extremely reactive clay) – articulation joints become critical at all building connections and bends.

  
  

3. At Changes in Direction

Where a drainage line bends or alters its direction, articulation joints are used to allow for controlled deflection. Without them, stresses build up at the bend and can fracture pipe walls or dislodge fittings.

4. On Long Pipe Runs

Even on relatively stable soil, long straight runs of pipe can experience settlement, thermal expansion, or soil shift. Installing articulation joints at prescribed intervals ensures the system can flex without breaking.

5. Near Tree Root Zones

Trees can exert pressure on underground drainage systems as roots grow and expand. Articulation joints are often installed in areas with mature trees or landscaping to minimise the risk of joint failure caused by root movement.

Why These Locations Matter

If articulation joints are missing in these key places, the risks include:

• Pipe fractures and leaks.

• Infiltration of groundwater into sewer systems.

• Blockages caused by pipe misalignment.

• Costly excavation and repair works.

By strategically placing articulation joints, the plumbing network remains watertight, durable, and compliant with AS/NZS 3500.2.

Prevention is Better than the Cure

Articulation joints are not just a design detail—they’re a compliance and protection measure. They’re needed:

• At building connections

• In reactive soils

• At pipe bends and changes of direction

• Along long runs

• Near trees and heavy landscaping

If you’re planning drainage works, always check your site classification report and ensure a RPEQ certified articulation report is submitted as part the plumber approvals.