Quick answer
In New Zealand you are allowed to replace your own kitchen mixer tap. The Plumbers, Gasfitters and Drainlayers Board lists repairing or replacing taps, ball cocks and plugs as work that does not need a licensed plumber, and a like-for-like swap in the same position does not need a building consent either. The pipe feeding the tap is a different matter: any pipe that supplies water is restricted work for an authorised plumber. Before you buy anything, check three things — the diameter of the hole in your benchtop (35mm is the New Zealand standard, but older holes are often larger), whether your hot water is low pressure or mains pressure, and whether the isolating valves under the sink still turn. If those valves are seized, a twenty-minute job becomes a house-wide shutdown, and that is a plumber's morning.
Key points
- The regulator lists repairing or replacing taps, ball cocks and plugs as work you can do yourself, but any pipe that supplies water is restricted — and the flexi hose sits right on that line.
- 35mm is the standard benchtop hole for a New Zealand sink mixer, and mixers cap the surface they will clamp to at around 50mm thick, so measure both before you buy.
- The tap is rarely what failed: it is usually the ceramic cartridge, the braided flexi hose, or an isolating valve seized open after a decade of never being turned.
- A mains-pressure mixer on a low-pressure cylinder makes the flow worse, not better, and needs an aerator swap and often a non-return valve to work at all.
- Kitchen sinks are deliberately excluded from the 50°C hot water limit that applies to basins, baths and showers, so a kitchen mixer is designed to run hotter.
The tap is yours. The pipe behind it isn't.
The tap in a Glen Innes rental had been dripping since March. The tenant mentioned it once, politely, then stopped. By the time anyone looked there was a soft patch in the base of the sink cabinet, the melteca had swollen along the bottom edge like a wet biscuit, and the drip turned out to be a worn cartridge — a part you can hold in one hand. Replacing a kitchen mixer is one of the few jobs in a kitchen the law genuinely leaves to you. That is not the problem. The problem is everything within 300mm of the tap you did not think you were touching.
What follows assumes a like-for-like swap: existing mixer, existing hole, same position. Move the tap, add a boiling-water outlet, or run fresh supply pipework and you are in different territory, and probably a plumber's. Everything here is checked against the regulator's own guidance, MBIE's building performance material, and a New Zealand manufacturer's installation sheet — because most of what surfaces in a search on this is British or Australian, and quietly wrong about the parts that matter here.
The law is clearer than you would expect
The Plumbers, Gasfitters and Drainlayers Board is the regulator, and its consumer guidance is blunt. Work you can do yourself includes installing dishwashers and washing machines, and replacing or repairing taps, ball cocks and plugs. No permit, no notification, no sign-off. The other half is the half people skip: a licensed plumber is required for fixing or unfixing any pipe, plumbing fixture or appliance — traps, waste, soil, vent and overflow pipes, and any pipe that supplies water. Read the two lists side by side and the line is obvious. The tap is a fitting you may change. The pipework feeding it is not.
You will find blogs asserting this only applies to the home you live in, so landlords are excluded. The Board's guidance does not draw that line — it frames tap work as low-risk work that is not restricted in the first place, rather than a concession handed to owner-occupiers. That is a real distinction, and it is not the same as us telling you it is settled; if your insurer will ask, ring the Board. Consent is a separate layer and also fine: Schedule 1 of the Building Act exempts replacing sanitary plumbing where a comparable component goes back in the same position. Landlords should read that alongside keeping on top of maintenance across a portfolio.
Measure the hole before you fall in love with a tap
This is the constraint nobody checks, and the one that sends people back to the shop. A New Zealand sink mixer installation guide tells you to cut a single 35mm diameter hole into the mounting surface. Not roughly 35mm — 35mm. Run the ranges at the main brands here and the same number keeps coming up, because the base ring, the seal and the mounting studs are sized around it.
Your existing hole may not be 35mm. Kitchens fitted before mixers took over often had three-hole sink sets, or a larger hole cut to suit whatever was fashionable. If yours is bigger than the new tap's base there is nothing solid to clamp against and nothing for the seal to seal to — you need a wider base, a matching base plate, or you are modifying the benchtop. Thickness bites too: the sheet we checked caps the mounting surface at 50mm, because studs are only so long, and a chunky stone top or laminate on a build-up eats that before you start.
Enlarging a hole is a separate job again. Drilling laminate exposes the particleboard core, and the raw edge has to be sealed or the top swells from the inside where you will never see it — the trade-offs between laminate and stone are worth a read before you pick up a drill. Stone is a fabricator's job: diamond core, water-fed, real risk of cracking a top that is already in. And since the internet keeps getting this wrong — engineered stone is not banned here. Australia banned it in 2024 and we did not follow; WorkSafe tightened the exposure standard for respirable crystalline silica, and MBIE consulted on options including a ban without adopting one. It is a dust-control question, not a legal one, and the position could change. If you are choosing rather than drilling, how engineered stone compares with laminate and solid surface covers it.
Four checks that decide whether the tap fits.
Pressure is what catches Auckland out
Plenty of Auckland stock still runs hot water off a low-pressure cylinder fed by a header tank in the ceiling — villas and bungalows through the isthmus, older places around Avondale and Onehunga, ex-state houses across the south. Cold comes off the mains at full pressure, hot arrives at a fraction of it. That is unequal pressure, and a mixer has to be set up for it or it will not behave.
Manufacturers build for this, which is why the sheet has a section nobody reads. On an unequal-pressure install you remove the filter washer from the hot inlet and fit a plain washer so the non-return valve can function, fit that valve to the hot inlet, and swap the flow-restricted aerator for the unrestricted one in the box. Skip those steps and the symptom is predictable: cold blasts, hot dribbles, and the tap gets blamed for something the installer did. The sheet we checked gives a minimum of 35 kPa and an optimum band of 35 to 500 kPa — under the minimum, no aerator trick saves it, and you are into a cylinder conversation rather than a tap one.
Two footnotes. Mixers are typically not recommended on uncontrolled heating systems such as wetbacks or solar units unless a tempering valve is fitted, so ask before you buy. And the Building Code's 50°C cap at personal hygiene fixtures — basins, baths, showers, for new fixtures from November 2024 — explicitly excludes kitchen sinks. Your kitchen tap is meant to run hotter than your bathroom one. That is design, not a fault.
The failure is almost never the tap
Work out what actually broke before you spend anything. A mixer is a body, a ceramic cartridge, some O-rings and an aerator. The body almost never fails. Everything else is a consumable — cheap, available, replaceable without taking the tap off the bench.
| Symptom | Usual cause | Fix | DIY or plumber? |
|---|---|---|---|
| Steady drip from the spout | Worn ceramic cartridge | Replace the cartridge, not the tap | DIY — it is part of the tap |
| Weeping at the base of the spout | Perished O-rings on the swivel | O-ring kit for that model | DIY |
| Handle stiff or grinding | Grit in the cartridge from unflushed lines | Flush the lines, replace the cartridge | DIY |
| Flow dropped off on both sides | Aerator clogged with debris | Unscrew and clean the aerator | DIY |
| Puddle in the cupboard, tap dry | Flexi hose weeping at the crimped end | Replace both hoses, not just the wet one | Grey zone — see below |
| Hot barely trickles, cold is fine | Mains-pressure mixer on a low-pressure cylinder | Correct mixer, aerator and non-return valve | Plumber territory |
| Valve under the sink will not turn | Isolating valve seized open | Replace the valve with the mains off | Plumber |
The flexi hose, and the number everyone gets wrong
Braided flexible hoses are the two silver umbilicals running from your tap tails down to the valves: rubber wrapped in a stainless braid, standard since the late 1980s, and they do not last forever. When one lets go it does not drip. It releases mains pressure into a cupboard, and if the house is empty it keeps doing that all day.
What is defensible: the same insurer put the working life of a flexible hose at around ten years, and listed the signs — kinks, bulging, rust and leaks. Manufacturers are stricter again about handling. Do not stretch or twist the hose, hold a minimum bend radius of around 35mm, and do not crush the hose or the swaged ends. That last one is how hoses die young: someone over-tightens the nut at the tap tail, distorts the crimp, and the failure starts on day one and finishes eight years later. Insurers generally cover a pipe that suddenly bursts, and generally do not cover damage that happened slowly.
So is replacing a flexi hose DIY? The restricted list includes any pipe that supplies water, and a hose supplies water. But you cannot replace a tap at all without disconnecting hoses, and the Board plainly permits tap replacement, so a strict reading cannot be right either. Our practical position: swapping the hoses that come with the new tap, at the tap tails, is what the guidance contemplates. Re-running the supply pipework behind the valves is not. If your job looks more like the second, get an authorised plumber and stop reading blogs about it, including this one.
Nine times out of ten the tap's fine. It's the hose, or it's a valve that's been sitting open since the house was built and now it won't budge.
The isolating valve that turns twenty minutes into a shutdown
Check this first; almost nobody does. Under the sink, on each hose, there should be a small isolating valve — a quarter-turn lever or a screwdriver-slot stop. Manufacturers assume they are there, and the sheet we checked recommends fitting them to both hot and cold. In plenty of Auckland homes they are not there at all. A valve that has sat open for fifteen years does one of three things when you finally turn it: it closes properly and your Saturday is fine; it closes but weeps past the seat, so you cannot work dry; or it does not move, and you are shutting the whole house down at the toby to change a tap. If the toby is seized too, that is a plumber's morning over a drip.
What goes wrong
The order of operations is the most common failure, and entirely self-inflicted: people buy the tap first and measure second. Grit is next. Installation sheets are emphatic that pipework must be flushed thoroughly before the mixer goes on, and that in-line filters go on both hot and cold to keep foreign particles out of the ceramic cartridge. Skip the flush after any work upstream and you drive a decade of scale and copper swarf into a brand-new cartridge. It feels gritty within a month, and the brand points at the sheet when you ring — they also recommend a licensed installer, which can bite even where the law does not. That is what what a kitchen warranty actually covers in New Zealand usually turns on: the claim fails on installation, not on the part.
Third is the seal at the base, and it is the quiet one. The tap sits on a base ring with a seal, and it is the installer's job to make sure it closes all the way around the hole. Miss it and water from around the sink tracks down the stud hole into the core of the benchtop, where nothing dries and nobody looks — laminate is moisture resistant, not waterproof. That is how a benchtop swells under a tap that was never leaking.
Fourth is finding the tap was the least of it. You get the mixer off, put your hand on the cabinet floor, and it gives. That is not a tap job any more — it is a rotted cabinet base, swollen door bottoms, possibly neighbours either side. Sometimes it is a repair. Sometimes it is the moment to weigh up whether replacing the doors instead of the whole kitchen stacks up, or whether turning a rental around between tenancies is the better call.
What to check before you start
- Turn both isolating valves off and on. If either is seized or weeps past, book a plumber before you touch the tap.
- Measure the hole from underneath — 35mm is the standard, but yours is whatever it is.
- Measure benchtop thickness at the tap against the maximum mounting thickness on the new tap's sheet.
- Establish whether your hot water is low pressure or mains pressure before you choose a mixer, not after you fit it.
- If you have a wetback or solar unit, ask about tempering before you buy.
- Check spout reach and height against your sink — a tall gooseneck over a shallow bowl splashes every time.
- Buy new flexi hoses as a matter of course, and fit them without stretching, twisting or crushing the crimped ends.
- Confirm the tap carries a WELS water efficiency label — mandatory for taps sold here, and the star rating tells you the flow you are buying.
Frequently asked questions
Do I need a licensed plumber to replace a kitchen mixer tap in New Zealand?
No. The Plumbers, Gasfitters and Drainlayers Board's consumer guidance lists replacing or repairing taps, ball cocks and plugs as work you can do yourself, alongside installing dishwashers and washing machines. What you cannot touch is any pipe that supplies water, or waste, soil, vent and overflow pipes — those are restricted to an authorised plumber. Your tap's manufacturer may still recommend a licensed installer, and that can affect your warranty even where the law does not require it.
What size hole does a kitchen mixer need, and what if my existing hole is bigger?
35mm is the standard bench hole across New Zealand sink mixer ranges, and installation sheets typically specify a single 35mm diameter cut-out. If your existing hole is larger — common where an old three-hole sink set was fitted — the new tap's base ring may have nothing solid to clamp and seal against. Your options are a mixer with a wider base, a manufacturer's base plate that covers the gap, or modifying the benchtop, which is a fabricator's job on stone.
How often should the braided flexi hoses under my kitchen sink be replaced?
Insurer guidance puts the working life of a braided flexible hose at around ten years, and many carry a date on the tag. The sensible rule is to replace both hoses whenever the tap comes off, regardless of how they look, because the failure usually starts inside the crimped end where you cannot see it. Look for kinks, bulging, rust or weeping at the fittings. It matters for insurance too: a sudden burst is generally covered, while slow damage traced back to a worn hose generally is not.
Why does my new mixer have almost no hot water flow?
Most likely you have fitted a mains-pressure mixer to a low-pressure hot water system, common in older Auckland homes with a header tank in the ceiling. Mixers usually need setting up for unequal or low pressure: fitting a plain washer at the hot inlet so the non-return valve works, fitting that valve, and swapping the flow-restricted aerator for the unrestricted one supplied. If your hot side sits below the tap's minimum operating pressure — often around 35 kPa — no adjustment will fix it, and you are into a cylinder conversation with a plumber.
Do I need a building consent, and does anything change if I am a landlord?
A like-for-like tap replacement in the same position falls under the Schedule 1 exemption for repair, maintenance and replacement of sanitary plumbing, so no building consent is required. Relocating the tap or altering supply pipework can change that answer, and engages the licensed-plumber requirement anyway. On the landlord question, the Board frames tap work as low-risk work that is not restricted, rather than an exemption limited to owner-occupiers — but do not rely on our reading of it. Ring the Board, and check your policy wording while you are at it.
When the tap is not the problem
Most of the time a dripping mixer is a cartridge, an afternoon and a trip to the plumbing merchant. Sometimes you get the tap off and find the reason the cabinet smells. If that is where you have landed — a soft cabinet base, swollen door bottoms, a benchtop lifting around the hole — that is our work, not a tap job. MTN Kitchens has been building and installing kitchens out of our own East Tamaki workshop for 23 years, better than 2,000 of them, and we turn out ten-plus a week.
Send us the scope — one sink cabinet, a whole kitchen, or every unit in a block — and we will come back inside 24 hours with a trade-priced number, plus GST. No showroom, so you are not paying for one. Supply and install sits under one contract and one invoice, so when something needs sorting there is one number to ring and nobody to point at. A rough description and a couple of photos are enough to price off.