The starting point
Section 40 of the Building Act 2004 says building work must be carried out under a building consent unless an exemption applies. Plumbing counts as building work for this purpose.
The plumbing and drainlaying exemptions are in Part 2 of Schedule 1, and the general ones don't help with a cylinder. Clause 32, which covers repairing and replacing sanitary plumbing, leaves out the "repair or replacement of any water heater (unless permitted under clauses 36 to 38)". Clause 35, on altering existing plumbing, likewise excludes "an alteration to a water heater".
The three clauses, word for word
- Repairs, clause 36. Schedule 1 lists "the repair or maintenance of any existing water heater using comparable building products or a comparable assembly" as exempt.
- Cylinders on a wetback or similar, clause 37. Exempt is "the replacement of any water-storage heater connected to a solid-fuel heater or other supplementary heat exchanger", but only where the replacement "is a comparable open-vented water storage heater" and "is fixed in the same position, and uses the same pipework, as the replaced water storage heater".
- Other replacements, clause 38. Exempt is "the replacement of any water heater (including the repositioning of an existing water heater) if the replacement water heater is connected to, or incorporates, a controlled heat source or, if connected to or incorporating more than 1 heat source, 2 or more heat sources all of which are controlled".
What those conditions mean in practice
An authorised person has to do it. The clauses sit in Part 2 of Schedule 1, which only covers work by a person authorised under the Plumbers, Gasfitters, and Drainlayers Act 2006. Section 42A of the Building Act leaves out anyone relying on that Act's householder or rural exemptions, or on the exemptions for unregistered people working under supervision (sections 15, 16, 19 and 25). A homeowner swapping their own cylinder can't lean on these exemptions.
The Building Code still applies. Section 17 says all building work must comply with the Building Code whether or not it needs a consent. Exempt work must also leave the building at least as compliant as it was, and not breach any other law.
"Controlled heat source" isn't defined in the Act. We found no definition in the Building Act text, and we couldn't read MBIE's guidance on these clauses, so we won't tell you which heaters count. Ask the plumber which clause they're relying on, and why.
Position and pipework only appear in clause 37. Rules of thumb about size and position aren't part of clause 38. Clause 37 is the one that mentions the same position and the same pipework, and it applies to cylinders on a wetback or other supplementary heat exchanger.
When the council decides, and when consent is needed
A council can decide that particular building work doesn't need a consent because the finished work is likely to comply with the Building Code (Schedule 1, Part 1, clause 2). That's its call, case by case, so if your plumber isn't sure an exemption fits, ask the council before work starts.
If a consent is needed, the owner applies for it, and once all the work is complete, applies to the council for a code compliance certificate (section 92).
Under the self-certification scheme, an endorsed plumber can certify some consented plumbing instead of a council inspection. The consent is still needed, the work must still comply, and the owner has to tell the council in writing the name of any endorsed plumber who will issue a certificate of compliance and wasn't named in the application.
Urgent replacements
Section 41 lets building work go ahead without a consent when one can't practicably be obtained in advance, because the work is urgent to save or protect life or health or to prevent serious damage to property. If that work would otherwise have needed a consent, the owner must apply for a certificate of acceptance as soon as practicable afterwards (section 42).
So a burst cylinder can be dealt with straight away, but the paperwork may still follow. See leaking cylinders for what to do first.
Gas and electrical parts of the job
Gasfitting is "energy work", which generally doesn't need a building consent (section 43), with some exceptions. It does need gas paperwork: a Gas Safety Certificate for all gasfitting once it's connected, and a certificate of compliance for general and high-risk gasfitting. Swapping a gas water heater for an equivalent one, with no change to the pipework, flue, pressure, gas type, ventilation or energy use, is low-risk gasfitting.
An electrician handles the electrical connection. Our guide to certificates of compliance explains the different documents.
Be wary of
- "You never need a consent for a cylinder." The exemptions come with conditions.
- A tradie who can't say which clause the job falls under.
- Anyone without a current PGDB practising licence offering to do it. Knowingly paying an unauthorised person to do sanitary plumbing is an offence in itself.
- A quote for a gas heater that says nothing about gas certificates.
Questions to ask the plumber
- Which clause of Schedule 1 does this job fall under, and why?
- In your view, is the new heater on a controlled heat source?
- We have a wetback. Will the new cylinder be a comparable open-vented one, in the same position on the same pipework?
- If a consent is needed, who applies, and who arranges inspections or self-certification?
- What paperwork will I have when it's done?
What we would do
Ask the consent question before you accept the quote, not after the old cylinder has gone. A good answer names the clause, explains why the job fits it and says what happens if it doesn't. If there's a wetback, a change to a different kind of cylinder or anything the plumber is unsure about, ring the council and ask. Then have an authorised plumber who specialises in hot water cylinders do the work, because none of these exemptions apply otherwise.