Our client insists every new Queensland home needs a rainwater tank, but the certifier says it depends on the council. What does the code actually require?

The certifier is right. There is no statewide rule that every new Queensland home must have a rainwater tank. The requirement only switches on where the local council has applied for and been granted a Ministerial approval that makes Queensland Development Code MP 4.2 mandatory in its area. "It depends on the council" is exactly how the code is built. [1]

Two instruments, two different jobs. Much of the confusion comes from treating these as one rule:

• NCC 2022 Volume Three (the Plumbing Code of Australia) has a Part B7 dealing with rainwater storage. [2] That is plumbing: how rainwater storage is handled when there is one. It is not the provision that decides whether a new house has to have a tank.
• QDC MP 4.2, Rainwater tanks and other supplementary water supply systems, is the Queensland instrument that decides when a tank or other supplementary supply must be installed for a Class 1 building. [1]

How the council switch works. Section 4 of MP 4.2 sets out the mechanism: [1]

• A local government may apply to the Minister for approval to require MP 4.2 to apply mandatorily to building development applications for new Class 1 buildings within a reticulated town water area.
• The Minister may grant the approval if satisfied it will result in a net benefit to the relevant community.
• An approval applies to building development applications lodged on or after the date it is granted.

So the real question for your client is not "does Queensland require a tank?" but three narrower ones: is the lot in a reticulated town water area, does the council hold a current MP 4.2 approval covering it, and was that approval granted before the building development application was lodged? If the answer to any of those is no, MP 4.2 does not make a tank compulsory.

Even where it applies, "required" does not automatically mean "tank". This is the misconception worth correcting on both sides. The performance criterion is that the house, in addition to its town water connection, is connected to a supplementary water source. [3] The acceptable solution can be met by connecting to any of: [3]

• a rainwater tank;
• a greywater treatment plant;
• a supplementary water supply system; or
• a combination of these.

Where a tank is the chosen route, the acceptable solution requires it to: [3]

• meet the minimum tank size for the dwelling type set out in Appendix A of MP 4.2, or in the council's approval;
• capture rainfall from the minimum roof catchment area in Appendix A, or in the council's approval; and
• be connected to the toilet cisterns and washing machine cold water taps, a fixture for external use, and any other fixture the council's approval specifies.

Note the "or": an approval can set its own numbers and add fixtures, so read the council's approval itself rather than relying only on the default table. The minimum sizes are not reproduced here; take them from Appendix A of MP 4.2 and cross-check the approval.

Practical next step. Ask the certifier which council approval they are relying on and its date, and check it against the lodgement date for the building development application. That settles the argument on paper rather than on opinion.

Edition note. Queensland is on NCC 2022 Amendment 2 until 30 April 2027, and NCC 2025 takes effect from 1 May 2027 with no election window. The Queensland Development Code applies alongside whichever NCC edition is in force. [4] NCC 2025 Volume Three keeps a Part B7 for rainwater storage [5], but whether current QDC settings carry over unchanged after 1 May 2027 is not yet confirmed. The MP 4.2 text relied on here is Version 2.0, published 15 January 2013, so confirm with the council or your certifier that no later version applies to your project.