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
What you need
- Bucket and old towels
- Plunger
- Multigrips (usually hand-tight is enough)
- Old toothbrush or bottle brush
- Gloves
- 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
The P-trap under the sink 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.