A new kitchen sink is one of the most satisfying upgrades in a renovation, and one of the most misunderstood jobs in the DIY world. Plenty of guides walk you through the whole installation as if it were flat pack furniture, and plenty of readers do not realise that in Western Australia, significant parts of the job are licensed plumbing work by law. So this guide does something slightly different. We will walk through the full process so you understand exactly what is involved, be clear about which parts you can legally do yourself, and explain why the licensed parts exist, because the rules are there for reasons we see proven weekly.
Where the legal line sits in WA
Western Australia has some of the strictest plumbing regulations in the country, and the short version is this. You can remove and install the sink bowl itself into the benchtop, assemble accessories and seal the sink to the bench. The moment the work touches the water supply or the drainage system, connecting taps, altering pipework, connecting or modifying the waste and trap, it becomes work for a licensed plumber. The penalties for unlicensed plumbing work are genuine, but the more practical point is insurance, because damage flowing from unlicensed work is a claim your insurer can decline, and a slow waste leak inside a sink cabinet can quietly destroy the cabinetry and floor before anyone notices.
Planning and measuring, the part that decides everything
Every smooth sink installation is won at the measuring stage. If you are replacing like for like, confirm the new sink’s cutout dimensions against the existing hole, remembering that a new sink smaller than the old cutout is a problem with no elegant solution. Check the bowl depth against the cabinet, deeper fashionable bowls sometimes collide with existing waste heights and require the drainage to be reworked lower, which turns a swap into a bigger job. Count your tap holes, confirm where the mixer will sit, and check that the existing isolation valves under the bench actually work, because discovering a seized valve with the old sink already out is a classic Saturday afternoon disaster.
What the removal and fit involve
The sequence itself is logical. Water is isolated and taps disconnected, the waste and trap are disconnected, the old sink’s clips are released and the sealant cut so the bowl lifts free. The bench edge is cleaned back to bare, the new sink is test fitted, the tap is mounted to the sink before it goes in because access is far better on the bench than under it, and the sink is sealed and clipped down. Then the licensed half begins, connecting the water supply with new flexible hoses or pipework, rebuilding the waste and trap to suit the new bowl configuration, and testing everything under pressure. Double bowl sinks, dishwasher connections and food waste disposers each add their own waste arrangements, which is exactly where home handiwork most often goes wrong.
The mistakes we get called to fix
A few patterns account for most of the failed DIY sink jobs we attend. Reused old flexi hoses that fail months later inside the cabinet. Traps assembled without fall or with doubled up seals that weep slowly into the cabinet base. Sealant used as a structural solution for a poorly fitting bowl. Dishwasher drain hoses pushed onto spigots without clamps, and no high loop in the hose, which lets sink water siphon back into the dishwasher. Each of these is invisible on day one and expensive by month six. The common thread is that supply and drainage connections look simple and are not, which is precisely why they are the licensed part.
The sensible division of labour
The arrangement that works, and the one we happily support, is a shared job. You choose the sink and tapware, handle the benchtop fit and the sealing if you are confident, and have a licensed plumber do the disconnection and the final connections. For us that connection work is typically quick, and it comes with tested joints, compliant drainage, new hoses and someone accountable if anything ever weeps. Compared to the cost of a ruined cabinet floor, or a benchtop cut wrongly, it is the cheapest part of the project.
Getting it done
If your kitchen upgrade includes a new sink, plan the measurements carefully, buy quality tapware and hoses, and book the licensed connections rather than chancing them. Our team handles sink and tap installations across Perth alongside our drainage work, and while we are under the bench we will happily check the state of your isolation valves, hoses and waste, the free plumbing health check that comes with every job. Call Drains Plus and get it flowing properly from day one.
One final planning note for older Perth homes. If your existing kitchen dates back decades, the pipework serving it may too, and a sink upgrade is the natural moment to deal with it. Original galvanised supply lines, corroded traps and wastes narrowed by years of grease all undermine a brand new sink’s performance from day one, and accessing them costs nothing extra while the cabinet is already open. Ask whoever does your connections to assess what is there before simply reconnecting to it, because reusing tired pipework under new fittings is the renovation equivalent of new shoes on worn out socks.
