Master Plumbers August FAQ: Do you know the answers?

Is having sanitary junctions on 15° in the standard?

Yes it is, as per AS/NZS 3500.2 Clause 4.9.1.2

Where a junction is used to make the connection of a DN 100 branch drain to another DN 100 drain, the entry level of the branch drain shall be elevated at an incline of not less than 15° above the horizontal. Reason for the change in the way we install junctions is a minimum of 15° above horizontal removes the probability of the partial backwash of a discharge into the branch causing stranding that can lead to blockages in the drain. In Victoria there is a variation for installations in suspended drainage, so make sure to check out the National Construction Code.

3500.0 glossary of terms defines branch drains as section of a drain that is intended to receive the discharge of fixture discharge pipes but which has a lower fixture unit loading and which may be of smaller nominal size than the main drain at its point of connection.

Do valley gutters have a minimum roof pitch they can be installed on?

Yes,

AS/NZS 3500.3 Section 3.6, discusses roof slopes shall not be less than 1:4.5 (12.5°).

When sizing up your valley gutter the nominal valley gutter side angle shall be 1:3.4 (16.5°). Discharge of valley’s shall only discharge to eaves gutters or box gutters with a minimum of 50mm overhang with the end of the valley turned down into the gutter. Valley gutters to be fixed with galvanised nails bent over or cleated at the outer edges of the gutter at intervals not exceeding 500 mm.

Where can I find the right information on backflow hazard ratings?

Hazard ratings for appliances and fixtures are no longer found in the 3500 suite, they can now be found in the National Construction Code (NCC) volume 3, more specifically schedule 41. This will cover all the ratings for individual, zone and containment protection. The NCC can be found online for free for anyone to view. Simply go to www.ncc.abcb.gov.au. If you are ever unsure what level of backflow protection you need for individual and zone, reach out to your relevant plumbing authority or your states Master Plumbers Association and they will be able to advise you on what is required to be installed. For containment protection reach out to your local water authority. Suitability of devices can be found in AS/NZS 3500.1 table 4.4.1