How to unblock a kitchen sink

A blocked kitchen sink is nearly always a grease problem. Fat goes down the drain warm and liquid, cools inside the pipe, and sets into a waxy layer that catches food scraps, coffee grounds and everything else that follows. Terry has been clearing sinks across Berala and Western Sydney since 1986, and the pattern rarely changes: the pipe narrows over months, drains slower and slower, then one Sunday night it stops entirely.

The good news is that a kitchen sink blockage usually sits close to the sink itself, in the trap or the first stretch of pipe, which means most people can clear it without any special tools.

Start with hot water and detergent

Squirt a generous amount of dishwashing detergent down the plughole, then follow it with a kettle of hot water. If your pipes are plastic, let the kettle sit for a minute first, since water straight off the boil can soften PVC joints over time. The detergent breaks the surface of the grease and the hot water re-melts it enough to move. Repeat two or three times. For a partial blockage this alone often does the job.

Plunge properly

If the sink has two bowls, block the second plughole with a wet rag, otherwise you are just pushing air back and forth between them. Seal the plunger over the drain with a few centimetres of water in the sink, then give it 10 to 15 firm, sharp plunges. The pressure wave does the work, not brute force. Run hot water afterwards to check the flow.

Clean out the trap

The curved section of pipe under the sink, the S-trap or bottle trap, unscrews by hand or with gentle pressure from multigrips. Put a bucket underneath first, because the trap holds water and usually a fair amount of sludge. Clear it out, check the pipe entering the wall for buildup you can reach, then refit it snugly. Hand-tight plus a quarter turn is plenty, since overtightening cracks the plastic nut.

What not to do

Skip the supermarket chemical drain cleaners. Caustic soda and similar products generate heat, damage older pipes and rubber seals, and often react with grease to form a hard soap plug that is worse than the original blockage. They also make the job hazardous for whoever opens the trap afterwards, because the pipe is now holding caustic solution. Plumbers can tell when a chemical cleaner has been poured in, and nobody enjoys that discovery.

When to stop

If the trap is clean and the sink still will not drain, the blockage is further down the line, sometimes at the point where the kitchen waste joins the main sewer. That is machine territory. A professional drain clear in Sydney generally lands between $150 and $350 depending on access and severity, and for a stubborn or repeating blockage a camera inspection will show exactly what is going on inside the pipe. A sink that blocks every few months is telling you something, usually a sagging pipe or root intrusion, and it is worth getting a licensed plumber onto it rather than buying a bigger plunger.