Kitchen · DIY guide
How to unblock a kitchen sink
Kitchen blockages are almost always congealed fat and food in the trap directly under the sink. Cleaning that trap is permitted maintenance in Victoria, and it solves the problem far more reliably than anything you can pour down.
Legal in Victoria — clearing traps and plunging is permitted maintenance
Checked as at September 2026. Rules and prices change — confirm anything you are about to act on.
What you need
- Bucket and old towels
- Plunger
- Multigrips (usually hand-tight is enough)
- Old toothbrush or bottle brush
- Gloves and eye protection
- Bicarb and vinegar
Step by step
Clear the cupboard and put a bucket underneath
Whatever is in that trap is coming out, and it will smell. Empty the cupboard completely and lay towels down before you touch anything.
Try the plunger first
Block the second bowl or the overflow if there is one — otherwise you are just pushing air around. Cover the plunger cup with water and use short firm strokes.
Open the trap
First, a stop: if any chemical drain cleaner has already gone down this sink, do not open the trap, do not plunge it and do not add anything else to it. Flush with plenty of cold water and tell a plumber what was used — caustic solution splashes at face height when a trap comes off. Otherwise the P-trap unscrews by hand in most modern installs. Loosen the top collar first, then the bottom, and let it drain into the bucket. Note the order of any washers as they come off.
Clean it out properly
Scrub the trap and the visible pipe ends with a brush. This is where the fat is. Rinse it in a laundry tub, not the sink you are working on.
Reassemble and test
Hand tight is correct for plastic traps — spanners crack them. Run the tap and watch the joints for a full minute before you put anything back in the cupboard.
Change the habit
Fat and oil should go in the bin, not the sink. A cheap sink strainer catches the rest.
Common mistakes
- Caustic drain cleaner — it sits in the trap and makes the next repair hazardous
- Overtightening plastic trap collars
- Not putting a bucket underneath
- Losing the sequence of the trap washers
When to stop and call someone
If clearing the trap does not fix it, the blockage is further down the line and that is licensed drainage work. Water coming back up into the sink from elsewhere, or affecting other fixtures, means the main line — not the trap.
This guide is general information, not advice for your particular house. Rules change — check the current position with the Building and Plumbing Commission, Energy Safe Victoria and WorkSafe Victoria before you rely on it. Plumbing, gas and electrical work must be done by a licensed practitioner. If your home was built or last renovated before 1990, assume asbestos until it is ruled out — see what a strip-out finds.