How to Fix a
Leaking Mixer Tap:
The Complete Sydney Guide.

A dripping mixer tap is one of those problems that feels minor until you see your water bill. A slow drip can waste up to 12,000 litres of water per year, according to the Australian Water Association. Multiply that across a kitchen tap and a bathroom tap and you have a genuine problem, not just an irritating noise.

The good news is that most mixer tap leaks are caused by a handful of worn parts, and replacing them does not require a plumber. This guide gives you everything you need to diagnose the exact type of leak, find the right part, and fix it properly the first time. We also tell you when the job crosses into licensed plumber territory, so you do not end up making things worse.

What Is a Mixer Tap and How Does It Work?

A mixer tap combines hot and cold water inside a single body before it exits the spout, giving you a single stream at your chosen temperature. You will find them in kitchens, bathrooms, and laundries across virtually every Australian home built in the last 30 years.

There are two main configurations:

• Single-handle mixer taps use one lever to control both temperature (left/right) and flow (up/down). Inside sits a single cartridge or ceramic disc valve that does all the work.
• Dual-handle mixer taps have separate hot and cold handles. Each handle has its own spindle, washer, and O-ring arrangement. When one side leaks, you generally only need to service that side.

Understanding which type you have matters because the parts and the repair steps differ. Look at your tap before you do anything else.

Step One Before Anything: Diagnose Where the Leak Is Coming From

The location of the leak tells you exactly what is failing. Do not skip this step. Replacing the wrong part wastes time and money, and the leak keeps going.

Tools and Parts You Will Need

Get these ready before you start. Having to leave mid-repair with water shut off is avoidable.

For most Australian tap brands (Caroma, Methven, Dorf, Meir, Vado, Oliveri), Reece Plumbing and Bunnings both stock cartridges. Take your old cartridge or a photo of your tap to the counter — staff can match it on the spot.

How to Fix a Leaking Mixer Tap: Step-by-Step

These steps cover both single-handle and dual-handle mixer taps. Where the process differs between the two, both are explained.

1. 1
   Turn off the water supply

   Locate the isolating valves beneath the sink. They sit on the hot and cold flexi hoses connected to the underside of the tap. Turn each one clockwise (right) until it stops — that is closed. If your tap does not have under-sink isolating valves, turn off the mains stopcock for the property (usually in the meter box or at the side of the house).

   • Turn the tap on fully after closing the valves to release residual pressure and confirm water flow has stopped.
   • Place your rag or bucket under the tap to catch the small amount of water left in the lines.
2. 2
   Remove the handle

   The handle is held by a grub screw that sits behind a small decorative cap.

   • Single-handle taps: prise off the plastic cover on top of the handle with a flathead screwdriver (it clips on). The grub screw sits underneath — use the correct Allen key size to loosen and remove it. The handle lifts straight off.
   • Dual-handle taps: each handle has a hot or cold indicator cap on top. Pop it off, then remove the grub screw below. Lift the handle off. If it feels stuck, do not force it — apply a small amount of penetrating oil around the base and wait 5 minutes.
   • Photograph the handle and orientation before removing it. Cartridges and ceramic discs are directional — if you reinstall them rotated 180 degrees the tap will work backwards.
3. 3
   Remove the cover and access the cartridge

   With the handle off, you will see either a chrome cover dome or a retaining nut securing the cartridge.

   • On taps with a cover dome: unscrew it by hand or with the adjustable wrench (wrap the jaws with tape to avoid scratching the chrome).
   • The cartridge or spindle assembly will now be visible. Use your adjustable wrench to loosen the retaining nut that holds the cartridge in place.
   • Once loose, pull the cartridge straight up and out. It should come out cleanly. If it is stuck, apply Inox or WD-40 around the base, wait a few minutes, and try again — never use excessive force or you risk cracking the tap body.
4. 4
   Identify what you are replacing: cartridge vs ceramic disc vs washer

   Now that the internals are exposed, you need to identify which valve type your tap uses. This determines what you buy and how you reinstall it.

   • Cartridge valve. A cylindrical plastic and rubber component, roughly 50–80mm tall. Common in single-handle mixer taps. If it feels gritty, has visible scoring, or the rubber seals are cracked, it needs replacing. Take it to the store — match by brand and cartridge height.
   • Ceramic disc valve (most common in modern taps). Two flat ceramic discs stacked inside a housing. The upper disc rotates when you move the handle; the lower disc is fixed. When either disc develops a hairline crack or the seating wears, you get a drip. Replace the entire disc cartridge as a unit — do not attempt to separate and clean individual discs, as they rarely seal properly once apart.
   • Rubber washer and O-rings (older taps). Common in older dual-handle taps and heritage-style tapware. The rubber washer sits at the base of the spindle and compresses against the tap seat when you turn the tap off. If the washer is flattened, cracked, or has a groove worn into it, replace it. Match the diameter exactly — a slightly undersized washer will not seal. Replace O-rings at the same time.
5. 5
   Install the new part

   • Lower the new cartridge or ceramic disc into position. Check that any alignment tabs or flat edges line up with the corresponding slots in the tap body — these prevent the cartridge from rotating.
   • For washer-style taps: seat the new washer onto the spindle's brass retaining screw and tighten it snugly. Do not overtighten — the washer should compress slightly but not deform.
   • Apply a thin layer of silicone plumber's grease to any O-rings before fitting them. This prevents tearing on installation and extends their service life.
   • Wrap 2–3 layers of PTFE thread tape clockwise around any threaded connections before reassembling. Pull the tape taut as you wind so it bonds to the threads.
6. 6
   Reassemble the tap

   • Refit the retaining nut and tighten with the adjustable wrench — firm, not brutal. Over-tightening cracks cartridge housings and warps ceramic disc seats.
   • Replace the cover dome or shroud, then slide the handle back onto the spindle in the same orientation you photographed in Step 2.
   • Reinsert the grub screw and tighten. Snap the cap back into place.
7. 7
   Test before you pack up

   • Slowly open the isolating valves beneath the sink (anticlockwise). Open them gradually, not all at once, to avoid water hammer.
   • Watch the base of the tap and the handle for any weeping as pressure restores.
   • Run both hot and cold through the full range of movement, then close the tap and watch the spout for 60 seconds.
   • If there is no drip: job done. If water is still weeping from the handle, the O-ring may not be seated correctly — re-open and check. If the spout still drips with a brand-new cartridge fitted, the tap seat is likely damaged. That is when you call a plumber.

Common Problems During the Repair (and How to Handle Them)

Seized or corroded components

Sydney's water supply is generally low in mineral content, but older taps can still develop scale or corrosion at connection points. Apply Inox or WD-40, wait 10 minutes, and try again. Use a strap wrench rather than grips on chrome finishes — grips will chew through plating. If a retaining nut will not budge after a second application of penetrating oil, stop and call a plumber rather than risk snapping the tap body.

Cannot find a matching cartridge

This happens with imported or discontinued tapware. Your best options: take the whole cartridge to Reece (they have an extensive cross-reference catalogue), search the brand name plus "cartridge" on tradelink.com.au, or contact the tap manufacturer directly — most Australian brands offer spare parts for 10 years after a product is discontinued. If parts are genuinely unavailable, it may be more cost-effective to replace the entire tapware fitting.

The drip comes back within weeks

If a new cartridge fixes the drip but it returns within a few weeks, the most likely cause is high water pressure. Sydney Water recommends a maximum of 500kPa at the meter; residential taps are designed for 200–350kPa. Pressure above this range accelerates cartridge wear dramatically. A licensed plumber can test your pressure and install a pressure-limiting valve if needed.

Persistent leak after replacing everything

A scored or pitted tap seat cannot be sealed by a cartridge or washer, no matter how new. The seat is the machined surface inside the tap body that the valve presses against. Re-grinding a tap seat requires a tap reseating tool and the skill to use it correctly. This is a job for a licensed plumber.

What Does It Cost to Fix a Leaking Mixer Tap in Sydney?

Here is an honest comparison between doing it yourself and calling a licensed plumber.

When You Should Call a Licensed Sydney Plumber

DIY is perfectly legal and sensible for cartridge, washer, and O-ring replacements. The following situations require a licensed plumber, and in NSW it is illegal to attempt them yourself:

• The tap seat is damaged. Re-grinding a seat requires specialist tools and is not a DIY-legal task in NSW.
• The flexi hose is cracked or bulging. Flexi hose failures are the leading cause of major internal water damage in Australian homes. Replace a cracked hose immediately — it is a licensed plumber job. See our full flexi hose guide.
• You cannot isolate the water supply. Attempting tap repairs without shutting off the supply risks flooding.
• The leak is coming from inside the wall or under the floor. This points to a pipe failure, not a tap problem.
• You are installing new tapware from scratch. Connecting new tapware to the supply lines is licensed work in NSW under the Plumbing and Drainage Act 2011.
• The repair has failed twice and the drip continues. A second failure signals a deeper issue that DIY cannot address.
• You cannot source the correct WaterMark-certified parts. Installing non-certified parts is a plumbing code violation in Australia.

Preventive Maintenance: Keep Your Taps Leak-Free for Longer

Most mixer tap leaks are predictable and preventable. These are the habits that extend cartridge and washer life significantly.

• Do not overtighten tap handles when turning them off. Forcing the handle past its stop crushes cartridge seals and is the fastest way to wear them out prematurely.
• Check under sinks for slow weeping at flexi hose connections every 6 months. A damp cupboard under the sink is a warning sign, not something to ignore.
• Test your water pressure annually. High pressure above 500kPa damages cartridges, O-rings, and flexi hoses across your entire home — not just one tap. A licensed plumber can test this in minutes.
• Replace flexi hoses every 10 years, or immediately if you see any braiding that is rusted, kinked, or bulging. Do not wait for them to burst.
• Flush aerators (the mesh screen at the spout tip) every 6–12 months. A clogged aerator increases back-pressure in the tap body and accelerates wear.
• If you are going on an extended holiday, turn off the isolating valves under every sink. It takes 30 seconds and eliminates the risk of coming home to a flooded kitchen.
• Lubricate O-rings with silicone grease (not petroleum-based grease, which degrades rubber) whenever you service a tap.

Frequently Asked Questions