TL;DR
- Kitchen mixer taps are not all the same size. The mounting hole in your sink or benchtop, the spout reach, and the connection thread all need to match your new tap before you buy it.
- Most modern Australian kitchens use a single-hole bench-mount setup with a 35mm mounting hole and a ½” BSP connection at the supply lines.
- The flexi hoses that connect the tap to your isolation valves are a separate decision: length, thread size, and WaterMark certification all matter.
- In NSW, connecting or disconnecting a mixer tap from the hot and cold supply is licensed plumbing work. It is not a DIY job, regardless of how straightforward it looks.
- Get the measurements before you shop. Getting them wrong means a second trip to the supplier and a job that takes twice as long.
The tap is dripping, the cartridge is shot, or you’re renovating and want something that doesn’t look like it came with the house in 1994. Whatever the reason, replacing a kitchen mixer tap sounds simple until you’re standing in a plumbing supply store being asked what connection type you need and you have no idea.
This guide covers what to measure, what to check under the sink, and what to tell your plumber before anyone buys anything.
Start under the sink, not in the showroom
The most common mistake when buying a replacement kitchen mixer is choosing the tap before checking what’s already there. A tap that looks perfect online can sit in a box for a week while you wait for an adaptor, or worse, it goes back because the mounting hole is the wrong diameter.
Before you look at any product, find out three things:
- How many holes does your sink or benchtop have?
- What is the diameter of the mounting hole?
- What type of connection is at the isolation valves under the sink?
Those three answers will eliminate most of the confusion before it starts.
Mounting holes: single, two-hole, or three-hole?
The number of holes in your sink or benchtop determines which tap styles will physically fit.
Single-hole mixers are the most common setup in Sydney kitchens built or renovated in the last 20 years. The entire tap body, including the handle and spout, mounts through one central hole. They’re practical, clean-looking, and easy to work with.
Three-hole setups use separate hot and cold handles with a central spout, each going through its own hole. They’re more common in older homes and traditional-style kitchens. If you want to swap to a single-hole mixer from a three-hole setup, the unused holes need to be covered with a deck plate or blanking plugs. That’s a separate step, and it affects how the finished bench looks.
Swapping like-for-like — single mixer for single mixer, or three-hole set for three-hole set — is always the simpler path. Changing the configuration adds work and sometimes cost.
The mounting hole diameter: 35mm is standard, but check first
Most modern kitchen sinks and stone or laminate benchtops in Australia are cut with a single mounting hole between 30mm and 35mm across, with 35mm being the size the majority of modern mixer taps are built to fit. If you’re replacing an existing single-hole mixer with a similar style, there’s a reasonable chance the hole size already works.
That said, it’s worth measuring before you buy, especially in these situations:
- The existing tap is older or an unusual brand
- The sink is a stainless undermount or farmhouse style
- You’re switching from a three-hole set to a single mixer
- The benchtop is stone (enlarging a hole in stone is a specialist job)
If the new tap needs a slightly larger hole, that can sometimes be adjusted in a timber or laminate benchtop. In stone, it’s a different conversation entirely, and usually one worth having before you order anything.
Bench-mount vs wall-mount: a different set of requirements
Most kitchen taps in Sydney homes are bench-mounted, meaning the tap body sits on the sink or benchtop and the supply lines come up through the cabinetry below. Wall-mounted kitchen taps are less common but do appear in renovation projects and European-style kitchens.
Wall-mounted taps have a different set of requirements. The supply lines are roughed into the wall at a fixed height and spacing, and the new tap needs to match that spacing exactly. If you’re switching from bench-mount to wall-mount, or the other way around, that’s a more involved job that goes beyond swapping the tap itself.
Stick to like-for-like on the mounting type unless you’re doing a full kitchen renovation with a plumber involved from the start.
Spout reach and height: the practical checks people skip
Two measurements that often get overlooked until the tap is installed:
Spout reach is the horizontal distance from the base of the tap to where the water falls. If the reach is too short, the water hits the front of the sink. Too long, and it sprays over the back or into a double-bowl divider. Measure from the centre of your mounting hole to the centre of the sink bowl. That’s the reach you need.
Spout height matters if you regularly fill tall pots or pitchers. A low-profile tap that looks sleek in the catalogue can be frustrating if you can’t get a stockpot under it. Check the clearance between the tap outlet and the sink base before you commit.
Connection types under the sink: what you’re actually dealing with
This is the part most homeowners don’t think about until the plumber is already there. Under your kitchen sink, the hot and cold supply lines terminate at isolation valves (also called mini-stops or quarter-turn valves). The tap connects to those valves via flexible hoses, commonly called flexi hoses or braided hoses.
There are two main connection scenarios you’ll encounter in Sydney homes:
Isolation valves already in place: Most kitchens built or renovated in the last 20 to 30 years will have quarter-turn isolation valves under the sink. The flexi hoses from the tap connect directly to these. This is the straightforward setup.
Older hard-copper connections: In older Sydney homes, the supply lines may run directly from the copper pipework without a proper isolation valve in place. In this case, isolation valves need to be fitted before the new tap can be connected cleanly. That’s additional work, but it’s also the right time to do it — having proper isolation valves under the kitchen sink is good practice regardless.
Thread sizes: the detail that trips people up
The connection between the flexi hose and the tap tail uses a threaded fitting. In Australian kitchens, the two thread sizes you’ll encounter are:
- M10 (10mm male thread) — the most common thread size on modern single-hole kitchen mixer taps in Australia. The flexi hose connects to the tap tail with an M10 fitting at the tap end.
- ½” BSP (British Standard Pipe) — used at the isolation valve end of the flexi hose in most Australian homes. This is the standard thread on mini-stop valves.
So a typical flexi hose for a modern Australian kitchen mixer runs M10 at the tap end and ½” BSP female at the valve end. The most common lengths are 300mm to 400mm, though longer options exist for deeper cabinetry or unusual layouts.
If your existing tap has copper tails rather than threaded connections, the setup under the sink may use compression fittings instead. A compression fitting uses a nut and olive (a small brass ring) to create a seal around the copper tube. Your plumber will identify what’s there and connect accordingly.
WaterMark certification: not optional
Any tap or flexi hose installed in an Australian home must carry WaterMark certification. WaterMark is the national product certification scheme that confirms plumbing products meet Australian standards for safety and performance. It applies to the tap body, the flexi hoses, and any fittings used in the connection.
This matters practically when you’re buying a tap. Products sourced from overseas, particularly online marketplaces, may not carry WaterMark. A licensed plumber in NSW should not install a product that lacks the certification, and if a non-certified product fails, your home insurance may not cover the resulting damage.
Buy Australian-stocked tapware from a reputable supplier, check for the WaterMark logo, and keep the product documentation. If you’re supplying your own tap for a plumber to install, confirm it’s WaterMark certified before the job day.
Water pressure compatibility: one more thing to check
Most Sydney homes run on mains pressure, which sits somewhere in the range of 200 to 500 kPa at the tap. Most modern kitchen mixers are designed for mains pressure and will work without issue.
Where it gets relevant is in older homes with gravity-fed systems (rare but they exist), or in some apartment buildings where the pressure is lower than expected. Some mixer cartridges require a minimum pressure to operate smoothly, particularly for balanced hot and cold flow. If you’ve had pressure issues with the existing tap, mention that to your plumber before choosing a replacement — some cartridge types handle low-pressure situations better than others.
It’s also worth noting that if your home has a pressure-limiting valve (PLV) set below the recommended range, a new tap won’t fix the underlying pressure problem. That’s a separate conversation.
What to measure and check before you buy: a quick reference
| What to check | What you’re looking for |
|---|---|
| Number of mounting holes | Single, two-hole, or three-hole |
| Mounting hole diameter | Typically 35mm for modern kitchens |
| Spout reach | Measure from hole centre to sink bowl centre |
| Spout height clearance | Will a large pot fit under it? |
| Mounting type | Bench-mount or wall-mount |
| Isolation valves present? | Quarter-turn mini-stops under the sink |
| Tap tail thread size | M10 on most modern Australian mixers |
| Flexi hose length needed | Measure from valve to tap tail with slack |
| WaterMark certification | Required on tap and hoses |
Can you replace a kitchen mixer tap yourself in NSW?
In NSW, connecting or disconnecting a tap from the hot and cold water supply is classified as plumbing work and must be done by a licensed plumber. The flexi hoses that run between the tap and the isolation valves are considered part of the water pipe system. This isn’t a grey area — it’s the law under the Plumbing and Drainage Act, and it applies regardless of how simple the job looks from the outside.
What you can do yourself is remove the old tap head or handle for cleaning, replace the aerator on the spout, or clean under the sink in preparation for the plumber’s visit. The actual disconnection, connection, and pressure testing needs a licence behind it.
The reason this matters beyond compliance: a flexi hose that isn’t properly seated, or a connection that isn’t pressure-tested after installation, can fail at mains pressure. Under a kitchen sink, that’s a significant volume of water in a short amount of time. It’s not worth the risk to save a callout fee.
If you’re unsure whether your existing setup has isolation valves, or you want to know what connection type is under your sink before buying a tap, a licensed plumber can check it in a few minutes and save you a wasted trip to the supplier.
Buying the tap before the plumber visits: a sensible approach
There’s nothing wrong with choosing and purchasing your own tapware before booking the installation. Many homeowners do it — you get to pick the style, the finish, and the brand without feeling rushed. Just make sure the tap is WaterMark certified, you’ve confirmed the hole size and mounting type, and you’ve got the product spec sheet available so the plumber can check the connection requirements before starting.
If you’re not confident about the measurements, it’s worth having a plumber take a look first. A quick assessment visit means you buy the right tap the first time, and the installation goes smoothly. Trying to return a tap that’s been partially installed is a headache nobody needs.
For more on what the repair side of a leaking kitchen tap involves before you decide whether to repair or replace, see our post on fixing a leaking tap without replacing it. And if you’re ready to book a kitchen tap replacement, our leaking taps service page covers what to expect from a Jasco visit.
The honest takeaway
A kitchen mixer tap replacement is a straightforward job when the right information is in place before anyone picks up a tool. Get the hole size, the connection type, and the spout dimensions sorted before you buy. Make sure the tap carries WaterMark. And book a licensed plumber to do the connection — it’s a quick job done properly, and it comes with the peace of mind that the work is covered.
If you’re not sure what you’ve got under the sink, give us a call. We can tell you what you need to know before you spend a dollar on tapware.