Bath waste connections

When installing a bath in a wet area, the waste connections must comply with the requirements of the National Construction Code (NCC) Series, whether or not there is a floor waste gully.

It's common in the building industry to remove central floor waste gullies from bathrooms and other wet areas. When installing plumbing and drainage in wet areas in class 1 residential buildings, plumbers need to be aware of a number of requirements.

The Building Code of Australia (NCC Volumes 1 and 2) states that bathroom floors in South Australia don't need to be graded to a floor waste gully as long as:

all vessels (eg plumbing fixtures) include inbuilt overflow protection
there is a permanent open trapped connection to the waste system (such as a toilet pan)
or
the floor drains to a floor waste within the shower area without ponding.

The Plumbing Code of Australia (NCC Volume 3) requires:

any pipework and fittings materials and products used, where required under Section G of the NCC, must have WaterMark^TM certification
compliance with provisions of the AS/NZS 3500 Sanitary plumbing and drainage standard.

Although a floor waste gully may not be required under the Building Code of Australia for draining floors in class 1 residential buildings if all vessels have inbuilt overflow protection, a floor waste gully may still be installed so plumbing installations meet the requirements of the Plumbing Code of Australia.

If there is no inbuilt overflow protection fitted on plumbing fixtures in wet areas and a floor waste gully is installed to meet Building Code of Australia requirements, the fall of the floor surface to the floor waste gully must comply with the NCC Volumes 1 and 2, including SA Variations and Additions.

Examples of bath waste connections

Figure 1: Bath waste discharging to outside disconnector gully

Diagram of a bathtub with inbuilt overflow protection plumbed into a 40/50mm diameter bath trap. The pipe is plumbed to an outside sanitary pipe with a grade that ensures it does not hold water. A 100mm diameter riser pipe is installed on the outdoor connection to the sanitary pipe.

Figure 2: Bath waste discharging to floor waste gully in shower compartment

Illustration of bath waste discharging to floor waste gully in shower compartment in accordance with AS/NZS 3500.2:2003 Appendix D – DN 40/50mm bath waste connecting to a 80x65mm shower floor waste gully (optional bath flexible connector must have grade and not hold water).

Figure 3: Bath waste discharging to a sanitary drain

Illustration of bath waste discharging to a sanitary drain in accordance with AS/NZS 3500.2:2003 Appendix D – DN 40/50mm bath trap and DN 65mm discharge pipe connecting to a vented drain (if the bath plug and washer does not have a removable type grate for cleaning purposes, an inspection riser needs to be installed on the discharge pipe and shall be raised to surface)

Figure 4: Bath waste discharging to a floor waste gully located in bathroom floor

Figure 5: Bath waste discharging to a floor waste gully connected to a shower channel

Figure 6: Bath waste discharging indirectly to the top of a floor waste gully under a bath – not permitted

Illustration of bath waste discharging indirectly to the top of a floor waste gully under a bath, which is not permitted in accordance AS/NZS 3500.2:2003 Clause 6.4.1 – each sanitary fixture and appliance shall have a trap or self-sealing device. The trap or self-sealing device shall be in the same room as the fixture and/or appliance that is serves and be accessible for cleaning purposes