A mixer tap that keeps dripping after the lever is fully closed almost always has a problem inside its ceramic cartridge — the one moving part that starts and stops the water. Either the cartridge’s ceramic discs have worn until they no longer seal, or a speck of grit or scale has lodged between them and is holding them fractionally apart. Those two causes cover most dripping mixers. Beyond them sit mains pressure high enough to batter the seals over time — and perished O-rings, though those show up as water weeping around the base of the tap rather than a drip from the spout.
The fix is a new cartridge or a new tap, and which makes sense turns on a fact most guides skip: there is no such thing as a standard mixer cartridge. Identifying and sourcing the right one is usually the expensive part of a repair. We’ll run the numbers further down, including the cases where a repair still beats anything we sell.
A mixer has no washers to change
Old two-handle taps seal with a rubber washer on a jumper valve, screwed down against a brass seat. The rubber hardens, the tap drips, you fit a fifty-cent washer and it’s good for another few years.
A mixer is different. Inside the body sits a cartridge holding two ceramic discs with ports cut through them. Lift the lever and the discs slide until the ports align and water flows; swing it sideways to blend hot with cold; close it and solid ceramic covers the ports. Nothing presses on a seat, and there’s nothing to re-washer.
Ceramic is hard-wearing — a decent cartridge often gives a decade of daily use — but when a mixer drips, you replace the cartridge or replace the tap.
The four usual culprits
A worn cartridge is the front-runner. Years of use eventually score the disc faces, and once a groove forms, water tracks through: a steady drip from the spout that ignores how hard you close the tap. Forcing the lever only wears the discs faster.
Debris and scale come second. Any disturbance to the supply — a burst main up the street, a new hot water system — can send fine grit through the pipes, and some of it ends up in the cartridge. Sydney’s water is fairly soft, so heavy limescale is rare here, but deposits still build, and one hard fleck between the discs produces the same drip as a worn cartridge. Rinsing and reseating the cartridge sometimes fixes it; just as often the grit has already scratched the ceramic and the reprieve is short.
High water pressure is the quiet one. Parts of Sydney sit well above the 500 kPa plumbers treat as the ceiling for new work, and constant high pressure is hard on cartridge seals, flexi hoses and everything downstream. Mains pressure also climbs overnight as demand falls, which is why a borderline cartridge can drip at 2am and hold by breakfast. If your pipes thump when a tap closes — water hammer — or several taps started dripping around the same time, get the pressure tested before blaming the tapware; a pressure-limiting valve is a cheap fix, and replacing tap after tap without it just feeds new cartridges to the same problem.
Worn O-rings are the odd one out, with a different symptom. They seal the joints in the tap body — the base of a swivel spout, under the lever — so when they perish you get water weeping around the base rather than a drip from the spout. The difference matters: a base leak runs into the cabinet or the benchtop cut-out, where it does quiet damage a spout drip never will.
What you can legally check yourself in NSW
Most work on a tap connected to the water supply is licensed plumbing work in NSW. The exception is genuinely minor maintenance — NSW Fair Trading’s guidance allows jobs like changing a tap washer or swapping a screw-on shower head. Diagnosis costs nothing and breaks no rules, so start there.
- Work out where the water is coming from: a spout drip points to the cartridge, weeping at the base or lever to O-rings, wetness under the sink to the flexi hose connections.
- Feel the drip. If it runs warm, the tap is passing on the hot side and quietly bleeding your hot water service too.
- Inspect the flexi hoses under the sink or basin. Rust spots or bulging braid is a separate, more urgent problem — a failed flexi doesn’t drip, it floods.
- Find the isolating stops under the sink and check they actually turn — the water has to shut off before anyone can work.
Swapping the cartridge itself is the murky one. Mechanically it’s the modern washer change — but it means opening up a fitting that runs at mains pressure once the water goes back on, and the conservative reading puts it in licensed territory; NSW Fair Trading’s guidance is the reference, and there’s a fuller breakdown in our guide to replacing a tap yourself in NSW. Everything beyond that — removing the tap body, disturbing the flexi connections, replacing the mixer — is licensed work, no grey area there.
There is no such thing as a standard cartridge
Here is the part the hardware aisle doesn’t mention. Ceramic cartridges are nowhere near interchangeable. A couple of common diameters exist, and some budget mixers take a generic cartridge — but stem splines, base ports and heights all differ. Phoenix uses one design, Methven another, Caroma another again, and within a single brand the cartridge often changes between models, sometimes between production years of the same model. There is no truly universal spare.
That shapes what a real repair involves. Step one is identifying the exact cartridge, which usually means dismantling the tap first — any markings left with the box years ago. Step two is sourcing it: for anything outside the current ranges, often a special order that takes days or weeks, while the tap drips on. Step three is the reassembly gamble. The cartridge seals against seats and O-rings in the tap body, and if those have hardened or scored too, the new cartridge sits on a worn surface and the drip returns.
By the time all three steps are done, it’s usually cheaper — and lasts longer — to fit a whole new mixer, which arrives with a fresh cartridge, fresh seals and its own manufacturer’s warranty covering the lot. That, plainly, is why our model is replacement rather than repair.
Should you repair the tap or replace it?
A note on our interest here: we sell and install new taps and we don’t run a repair service, so when we say a repair sometimes wins, we’re arguing against our own invoice.
Check the current price and availability of the cartridge that matches your mixer. Caroma, Methven, Dorf and Phoenix generally keep spares available for current and recent models. Add a plumber’s time and a call-out fee — sometimes across two visits, one to identify the part and one to fit it — and the repair routinely lands well north of the part. Installation only for a mixer you supply costs $180 with no call-out fee; supplied products show their own complete installation total: tap, delivery and installation by a licensed plumber. A new basin mixer supplied and installed can cost less than the quote to repair the old one.
Three questions settle which way to jump:
- Can you name the cartridge? A current model from a brand that stocks spares is identifiable and days away; a no-name or discontinued mixer means the repair starts with paid detective work.
- Is the body worth more than the visit? A premium mixer that would cost a few hundred dollars to match deserves a cartridge; a low-cost budget mixer doesn’t.
- Is the cartridge the only thing wrong? A pitting finish, a sloppy swivel spout or ageing flexi hoses are more repairs queued behind this one.
Three yeses and repair wins: you keep a better tap than the repair money would buy, and it stays out of landfill. Any no, and replacement is the honest answer — spending serious repair money to resuscitate a tap that owes you nothing is sentiment, not economics, and the same money buys a mixer whose cartridge will still be identifiable in ten years.
If replacement is the answer, the fixed rates are on our tap installation cost page — each eligible extra mixer fitted in the same visit costs $50, not another full fee. If you’ve already bought a mixer you like, our bring your own tap service will fit it for $180. Either way, the installation carries our 12-month workmanship warranty, the tap carries its manufacturer’s warranty, and your Australian Consumer Law rights sit over the top of both.
The drip is going through your meter
A dripping mixer runs around the clock, and every drop crosses the water meter, so it adds a little to each quarterly Sydney Water bill. It stings twice on the hot side: a warm drip is water you paid to heat, trickling away all night while the system reheats behind it. Not a reason to panic — just a reason not to let it drift into next year.
If the diagnosis comes back terminal, the replacement doesn’t need to become a project. Every kitchen mixer and basin tap on our site is priced with delivery and licensed installation included, you pick an arrival window at checkout, and our install days include Saturdays and Sundays. If you’re not sure what to buy, start with our guide to choosing a kitchen tap. The drip stops the day the new tap goes in.
