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Changes to AS/NZS 3500.2:2018 Junctions in graded drains

Changes to the National Construction Code (NCC) 2019 included amendments to the Plumbing Code of Australia (PCA) Volume Three and this includes adoption of the 2018 version of AS/NZS 3500.2 Sanitary plumbing and drainage. One of the changes to AS/NZS 3500.2 has been a restriction on the use of 88o sweep junctions.

 Changes to AS/NZS 3500.2 in detail 

Essentially, the use of an 88° sweep junction (or ‘curved square’ junction) is no longer permitted for use in any position along a graded drain as a Deemed-to-Satisfy Solution under the new edition of AS/NZS 3500.2. 

Under the new edition of AS/NZS 3500.2 the only acceptable method of construction to connect a graded branch drain to a graded main drain is to use a 45° junction, a maintenance shaft or an inspection chamber. The projected areas of the graded branch drain and the opening to the graded main drain must not overlap. 

This requirement extends to unequal junction sizes as well (for example, where a DN 50 meets a DN 90) and must continue to provide for the main drain soffit 10mm lower than the invert of the branch drain. 

What about stack connections? 

Should a branch, discharge or fixture pipe connect to a stack, the use of a square, sweep, 45°, aerator, ball or double 45° / sweep is still permitted. However, the restricted zones per AS/NZS 3500.2:2018 (Fig / Table 6.7.3.2) still apply unless a lower pipe adjoins the stack under an opposing pipe at 45°. 

It is important to note that: 

  • using square junctions in a drain must still meet AS/NZS 3500.2:2018 (4.9.3) 
  • a concrete support base (min. 100 mm thick) is still required under all risers brought to the surface, underneath square junctions and under any 45 o junction, rising to the additional 45o junction 
  • Double junctions (either 45° or sweep) cannot be used to connect drains on-grade for a Deemed-to-Satisfy Solution. 

Can an 88° sweep junction still be used? 

A sweep junction may still be used to connect a graded drain to a vertical riser and as the base of a raised inspection opening. 

Further, given the changes are to AS/NZS 3500.2, which is referenced as a Deemed-to-Satisfy means of meeting the NCC, the use of an 88° sweep junction could potentially still be considered as part of Performance Solution to demonstrate compliance with the NCC Performance Requirements, but this would need to be subject to acceptance by the approval authority on an individual case-by-case basis. 

State and territory variations 

It is also important to check with your local authority or administration for any specific state or territory provisions that may override the PCA or AS/NZS 3500.2 provisions. 

You should also check with your local authority or administration regarding transitional arrangements and to what version of the NCC, PCA and, in turn, AS/NZS 3500.2 applies to your project. 

Further information on the changes

Given the nature of these changes, it’s recommended that builders discuss these changes with their relevant plumber and/or those preparing your sanitary plumbing designs. 

The Western Australian Department of Mines, Industry, Regulation and Safety has produced a useful technical note outlining the changes in more detail. 

You can access further information on the changes to the Plumbing Code of Australia (PCA) 2019 at  the ABCB website

To find out more, contact HIA’s Building Services team.

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