Bathroom renovations cross every trade in residential building — but plumbing is the one where the consequences of a bad tradesperson follow you for decades. A leak inside a wall behind new tiles is the single most expensive failure mode in this kind of work. Which is why the question 'is your plumber a Master Plumber' deserves a clear answer, not a hand-wave.
§01What 'Master Plumber' actually means in NZ
The Master Plumbers, Gasfitters and Drainlayers New Zealand programme (master-plumbers.org.nz) is a voluntary professional body — not a licensing body. Every working plumber in NZ has to be certified by the Plumbers, Gasfitters and Drainlayers Board (PGDB), which is the legal licensing requirement. Master Plumbers status is one tier above that — it requires the business to meet additional standards on training, insurance, complaint handling and the Master Plumbers Guarantee.
§04What the Master Plumbers Guarantee covers
Up to $20,000 of warranty coverage on the plumbing work for two years post-completion, payable directly through the Master Plumbers organisation if your plumber's business goes under during the warranty period. This is not a small detail — small plumbing businesses do close, and a warranty that depends on the business still existing is worth less than one backed by the trade body.
§06How your renovator usually books the plumber
Most bathroom renovators work with one or two preferred plumbers — relationships built up over years of jobs. That's good for you (the trades know each other's work) and bad for you (you're trusting the renovator's judgement on plumber quality). Ask, in writing, who their plumbing subcontractor is, whether that subcontractor is a Master Plumber, and request a copy of the PGDB certification number for your records.
§08Other paperwork worth asking for
- PGDB plumbing licence number (legally required)
- Master Plumbers membership (voluntary, recommended)
- Public liability insurance certificate (minimum $2M)
- BRANZ-tested waterproofing system the membrane installer uses
- LBP (Licensed Building Practitioner) registration of the lead builder
- Site Safe certification for any work involving structural change
- Council consent paperwork for any plumbing alteration or layout change
§10Red flags
If the renovator can't or won't tell you who is doing the plumbing, walk. If the plumbing is being done by 'the builder' rather than a separately certified plumber, walk — that's not legal in NZ for anything beyond very basic work. If nobody can produce the BRANZ-tested membrane name in writing, walk. These three questions will eliminate roughly 30% of the cheap end of the market — which is a feature, not a bug.