Tundish installation

This advisory note outlines the general installation requirements when connecting tundishes.

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Note	14/2021
Date issued	July 2021
Last updated	July 2021
For	Licensees / Contractors / the Plumbing and Drainage Industry
Issued by	Building Commission NSW Building Specialist Compliance Unit
Scope	Applies to all metropolitan and regional areas in NSW

Issue

During recent audits of Class 2 buildings by the Building Commission NSW Building Specialist Compliance Unit (BSCU), tundish installations are frequently installed in a non-compliant manner.

The following advisory note has been prepared to remind the industry of the general installation requirements regarding the connection of tundishes set out in AS/NZS 3500 Part 2, clause 13.21. Some additional referenced clauses have been listed to further help clarify the connection of tundishes to floor wastes.

Detail

13.21 Connection of tundishes

Tundishes may be connected—

to a waste pipe, not smaller than DN 25, in accordance with Clause 4.6.7.8
to a trapped waste pipe, not smaller than DN 40, in accordance with Appendix B, or
to a fixture trap.

When the tundish and discharge pipe is connected to a fixture trap—

the connection shall be made above the level of the water seal, and
the top of the tundish shall be above the flood level rim of the fixture.

Pipes discharging over a tundish shall have an air gap of a size at least twice the internal diameter of the discharging pipe.

Tundishes shall be accessible.

Considering AS3500.2, here are 3 common non-compliances related to tundish installations serving a condensate line that have been observed:

Non-compliant example 1

Incorrect tundish connection - example 1

Installation does not comply with AS3500:2 c.13.21

Non-compliant example 2

Incorrect tundish connection - example 2

Installation does not comply with AS3500:2 c.4.6.7.3, c.13.21

Non-compliant example 3

Incorrect tundish connection - example 3

Installation does not comply with AS3500:2 c.4.6.7.3, c.6.5.1, c.13.21

4.6.7.2 Discharge to floor waste gullies

Fixtures listed in Table 4.6.7.2, and fixture pairs in accordance with Clause 6.5.4, may be connected to floor waste gullies and, except for tundishes, shall be located within the same room as the gully.

Table 4.6.7.2: Discharge to floor waste gullies

Waste fixture	Maximum length of waste pipe m
	Connected to riser of floor waste gully		Connected to submerged inlet floor waste gully (see Figure 4.6.7.2)
	Fixture untrapped	Fixture trapped	Fixture trapped or untrapped
Tundish (see Clause 4.6.7.8)	10.0	10.0	10.0

Note: Floor waste gullies or similar traps directly connected to the drainage system and subjected to infrequent use shall be provided with an approved means of maintaining their water seals.

4.6.7.3 Connection of fixtures

Each fixture or fixture pair that is connected to a floor waste gully shall be connected by a separate waste pipe at a grade of not less than 2.5% and with a length not exceeding that specified in Table 4.6.7.2.

4.6.7.8 Discharges from tundishes

In addition to the discharges specified in Table 4.6.7.2, tundishes receiving discharges from water heater drains, air-conditioning units, other condensate lines, and the like, may discharge to a floor waste gully. The maximum length of the unvented discharge pipe shall not exceed 10m.

It is important to also note the clause and table excerpts from AS3500:2. Some examples of compliant installations are shown below:

Compliant example 1

Diagram of compliant tundish installation - example 1

Compliant example 2

Diagram of compliant tundish installation - example 2

Compliant example 3

Diagram of compliant tundish installation - example 3

Compliant example 4

Diagram of compliant tundish installation - example 4

Compliant example 5

Diagram of compliant tundish installation - example 5

Compliant example 6

Diagram of compliant tundish installation - example 6

6.5.1 General

Information contained within this advisory note refers to codes and standards current at the time at when it was last updated.

Building Commission NSW disclaims any liability (including for negligence) to any person in respect of anything done, or not done, by that person in whole or partial reliance on any of the information in this advisory note.

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