How to Replace a Mixer Tap Cartridge
I had a client in Indooroopilly last year who’d been to Reece three separate times trying to find the right cartridge for her Methven kitchen mixer. Each time she’d come back with one that almost fit but not quite — the diameter was off by a millimetre or the orientation tab was on the wrong side. By the third visit the bloke at the trade counter recognised her and asked, gently, whether she’d brought the old cartridge in. She hadn’t. She’d been measuring with a ruler off photos. The fourth visit she brought the part. Five minutes later she walked out with the exact match. Look mate, the rules of this job arent complicated, but the rule that catches everyone is this: take the old cartridge to the shop. I’ve seen this go wrong more times than I can count.
Quick legal note up front. Replacing the cartridge inside an existing mixer tap is homeowner-legal under the maintenance provisions of the Plumbing Code of Australia and AS/NZS 3500, as long as you don’t disturb the body of the tap or the supply pipework. Your swapping a wear part inside a fitting that’s already installed. What is NOT homeowner-legal: replacing the entire tap body, modifying supply lines, or doing any work where you’ve cut into a wall or floor to access pipework. Stay inside the cartridge swap and your fine. Cheaper to do once.
The other thing worth knowing: every old internet guide teaches washer-tap repair, but the modern Aussie home has almost no washer taps left. Mixer taps — the single-lever ones that do hot, cold and temperature blend on one handle — have replaced them everywhere. They don’t have washers, they have cartridges. The cartridge IS the wear part. When your mixer drips, leaks at the spout, or won’t shut off properly, your swapping the cartridge, not a washer. For traditional washer taps see our replace leaking tap washer guide instead.
What you’ll need
- Allen key set — the handle grub screw is usually 2 mm or 2.5 mm. Exact-fit matters or youll round the head.
- Adjustable shifter (250 mm)
- Pliers — long-nose for fishing out broken bits if it comes to that
- Replacement cartridge — brand-specific, sized to your tap (see Step 1)
- Old towel and bucket
- Vernier caliper or a ruler with mm markings for measuring the old cartridge
- Phillips #2 screwdriver
- Small smear of plumbers silicone grease — Selleys or Permatex. NOT vaseline, NOT WD-40.
- Camera phone — take photos of every step before you disturb anything
Step 1: Identify the tap brand
Look on the underside of the spout, on the tap body, or on the back of the lever — there’s usually a brand mark (Methven, Caroma, Phoenix, Mizu, Dorf, Mondella, Posh, Sussex). Note the model name if there is one. Brand-specific cartridges are stocked at Reece, Tradelink and Bunnings — but you need the brand to find the right part. Heres where most people go wrong: they assume cartridges are universal. They’re not. Methven cartridges don’t fit Caroma taps and vice versa.
Step 2: Turn off the water
For kitchen and bathroom mixers, there should be isolation valves under the sink or in the cabinet — small chrome valves on the hot and cold flexi hoses. Turn both clockwise to off. If there are no isolation valves, you’ll need to turn off the main water at the meter. Open the tap fully to bleed pressure and confirm both sides are off — water should stop within a few seconds. If it keeps running, one isolation valve isn’t fully closed.
Step 3: Remove the lever handle
Most mixer levers have a small grub screw on the underside or back of the lever, hidden under a plastic plug or coloured indicator cap (red/blue). Pry the cap off with a fingernail, then loosen the grub screw with the right-size Allen key. Don’t fully remove the grub screw — just loosen it enough to slide the lever off the cartridge spindle. Lever lifts straight up. If its stuck, a drop of CRC, ten minutes wait, then try again.
Step 4: Remove the decorative cover and dome
Under the lever you’ll see a chrome dome or skirt covering the cartridge. Some unscrew by hand, some need a strap wrench or a soft-jaw spanner. Take a photo before unscrewing so you can see the order of components. Don’t use ordinary pliers — they leave teeth marks on chrome you can’t polish out. Strap wrenches are $15 at Bunnings and worth owning if you’ve got chrome anywhere in the house.
Step 5: Unscrew the cartridge clamping nut
The cartridge is held in place by a brass nut threaded around the cartridge body. Use the shifter to undo it, anti-clockwise. This nut can be tight after years in service. If its seized, a small splash of CRC penetrating spray and a few minutes wait usually frees it. Don’t go gorilla on it — the brass tap body underneath cracks under excessive torque, and that’s a whole-tap replacement (licensed work).
Step 6: Pull the old cartridge straight out
With the nut off, the cartridge lifts straight up. It may need a wiggle — old O-rings sometimes stick to the tap body after years of mineral build-up. Don’t lever it sideways with a screwdriver because you’ll score the seating surfaces and create new leak paths. If its truly stuck, gentle long-nose pliers on the spindle, pulling straight up with a slight twist.
Step 7: Measure the old cartridge — this is where most people go wrong
Now the Aussie gotcha. With the old cartridge in your hand, measure the diameter of the cylindrical body (NOT the spindle) with the caliper. 35 mm and 40 mm cartridges look almost identical to the eye but a 40 mm wont fit a 35 mm seat and vice versa. Also note: some cartridges have flat sides or a cut-out on the bottom that engages with the tap body — that orientation matters too. Take the OLD cartridge to Reece, Tradelink or your nearest plumbing supplier and ask them to match it. Don’t try to identify it from a photo — bring the part. Cheaper to do once.
Step 8: Inspect the tap body before fitting the new cartridge
Look down into the tap body where the cartridge seats. Wipe out any mineral scale or grit with a clean rag wrapped around your finger. Smell for any rotten-egg sulphur smell — if its there, you’ve got biofilm in the tap body, and a quick wipe with metho on a rag clears it. Lubricate the new cartridge’s O-rings with a thin smear of plumbers silicone grease — this stops them tearing as the cartridge slides into place.
Step 9: Install the new cartridge
Drop the new cartridge into the body in the same orientation as the old one — this is where your photos pay off. It should drop straight in until it seats. If its not seating, you’ve either got the wrong size or the orientation tab isn’t aligned. Don’t force it. Hand-tighten the brass clamping nut, then a quarter-turn with the shifter — too tight cracks the cartridge body or the tap body. Quarter turn means quarter turn.
Step 10: Reassemble and test
Reinstall the dome or skirt, then the lever. Tighten the grub screw and replace the indicator cap. Slowly open the isolation valves under the sink. Operate the lever — should move smoothly through hot and cold, no drips at the spout, no leaks at the cartridge nut. Run hot and cold to full temperature for 60 seconds each. Wipe everything dry, wait 5 minutes, then check again with a dry tissue. Any moisture at the cartridge joint means under-tightened nut or a damaged O-ring. For related wet-area maintenance see our re-silicone bathroom guide.
When to call a tradie
Heres where the legal line sits. Cartridge swap on an existing mixer — homeowner DIY in every Australian state under the maintenance provisions of AS/NZS 3500. NOT homeowner DIY: replacing the entire tap body (that’s licensed plumber work because it involves disturbing the supply connection), modifying or replacing supply lines, any in-wall work, any work on flexi hoses (licensed in QLD, NSW and VIC). If the tap body itself is cracked, if you’ve stripped the clamping nut threads, if the spout is leaking from inside the wall — that’s me on the end of the phone. The cartridge replacement is genuinely a maintenance job; everything beyond it is restricted. Cheaper to do once.
Common screw-ups
- Wrong size cartridge. 35 mm and 40 mm look the same; they’re not interchangeable. Take the part to the shop.
- Cartridge rotated 180°. Hot and cold are swapped after install. Pull, rotate, reseat. Look for the orientation tab.
- Over-tightening the clamping nut. Cracks the cartridge body or the tap body. Hand-tight plus a quarter turn.
- WD-40 or vaseline on the O-rings. Wrong product. Plumbers silicone grease only.
- Buying online from a cartridge size guess. Seperate sizes look identical in photos. Always take the old part to the counter.
Cost & time
Brand-specific cartridge: $25–$95 depending on tap brand (Methven and Mizu are higher; Caroma and Mondella lower). Time: 30 minutes for a confident first-timer with the right part in hand, an hour if its your first tap job and you need to puzzle the dome off. Compare with a plumber callout: $180–$250 plus parts in southeast QLD. Genuine savings.
The Tomo rule — wrap
Measure before you buy, or take the old cartridge with you. 35 mm and 40 mm are NOT interchangeable, and there is no universal cartridge across Methven, Caroma, Phoenix and Dorf. Reece will help if you bring the part. Buying online by guessing the size is how you end up doing the job twice. And the modern equivalent of the washer fix is the cartridge swap — bin the 1980s tap repair guides because they dont apply to your kitchen mixer. Got a mixer still leaking after a cartridge swap, or a tap body that’s actually cracked? Send us a write-up and well help you sort whether its DIY or a licensed call.
