When it's an installation, not a swap
- A new build, a renovation or an extension that needs its own hot water.
- A second cylinder for a sleepout or a bathroom at the far end of the house.
- Moving the cylinder out of a cupboard, or outside.
- Switching to a type that needs a different site, such as a heat pump.
- Hot water for a granny flat.
What the Building Code asks of every installation
Clause G12 of the Building Code describes how the finished installation must perform. It has to avoid the likelihood of leaks, give reasonable access to parts that will need maintenance, and let the system be isolated for testing and maintenance.
The cylinder needs safety features that relieve excessive pressure and limit temperature. Hot water at basins, baths and showers must be delivered at a temperature that avoids the likelihood of scalding, and the installation must be capable of being controlled to prevent Legionella growth.
The Acceptable Solution for this clause, G12/AS1 Amendment 14, has been current since 1 November 2024, so older guides may quote superseded detail.
Consent: installing is not the same as replacing
Building work needs a building consent unless an exemption applies. Schedule 1 clause 38 exempts replacing a water heater, or repositioning an existing one, when the replacement is connected to or incorporates a controlled heat source and an authorised person does the work.
A first cylinder in an extension or a new build isn't a replacement, so that clause doesn't describe it. Expect your installer or the council to work out whether a consent is needed, and budget time for it if so. A council can also decide that particular work doesn't need a consent, case by case.
Granny flats have their own rule. Since 15 January 2026, a single-storey stand-alone dwelling of 70 m² or less can be built without a building consent if it meets Schedule 1A, and it must have no uncontrolled water heating. Ask the installer how the cylinder you choose meets that.
How an installation usually runs
Site visit
A plumber will look at where the cylinder can go, how the water and drain pipes will reach it, and what power or gas is close by.
Pick the cylinder
Type, pressure and capacity follow from the site and the household. Our sizing guide is a good start.
Sort the consent first
If one is needed, it is granted before work begins. Where the plumber is an endorsed certifying plumber, eligible consented plumbing can be self-certified instead of inspected by the council.
Install and connect
The plumber fits, restrains and plumbs the cylinder. An electrician makes the electrical connection, or an authorised gasfitter connects the gas.
Close it out
For consented work, you apply to the council for a code compliance certificate once everything is done. Gas work comes with a Gas Safety Certificate, and general gasfitting also needs a gas certificate of compliance.
Paperwork and contracts
Under self-certification, the endorsed plumber must lodge their certificate of compliance with the PGDB and give it to you, with the supporting documents, within 10 working days of finishing. Include it with your code compliance certificate application, or the council can refuse the CCC for that work.
For residential building work of $30,000 or more including GST, the contractor must give you a disclosure statement and checklist before you sign, and the contract must be written. Every residential building contract, written or spoken and of any value, carries implied warranties, and you can notify defects within 12 months of completion.
Since 2 May 2026, new building work, consented or not, must use lead-free plumbing products in drinking-water systems. It isn't retrospective, so it doesn't make your existing fittings illegal. Our main hot water cylinders page compares cylinder types.
Planning you can do, work you can't
You can
- Decide where you'd like the cylinder and measure the space.
- Find out whether the house has piped gas or would rely on bottles.
- Ring the council early if you're unsure whether a consent is needed.
- Keep every certificate together, in one folder.
Leave to an authorised tradie
- Pipework, valves, drains and the cylinder itself.
- Restraint and support for the cylinder.
- The power connection (an electrician) or gas (an authorised gasfitter).
- The plumbing details for any consent application.
Questions for your installer
- Does this installation need a building consent, and who applies for it?
- Are you endorsed to self-certify, or will the council inspect?
- Who will connect the power or gas?
- Which certificates and warranty papers will I get at the end?
- Will we have a written contract?
What we would do
Settle the location before anything else, because it decides the pipe runs, the power or gas, and often the consent question. Ask a cylinder installer to visit before you choose a model, and get their answer on consent in writing.