Blocked kitchen sink: causes, safe fixes and when to call

What it usually means — most likely first

1. Grease and food scraps in the sink’s own waste. Cooking fat, oil, dairy and starchy scraps coat the pipe until the water can only trickle through. If only the kitchen sink is slow, this is the most likely answer.
2. Build-up in the trap under the sink. The bend under the sink catches scraps, coffee grounds and the odd teaspoon.
3. Grease set further along the line. Kitchen waste often runs a long way to meet the main drain, and grease builds up wherever the pipe is coldest or flattest.
4. Grease on top of a pipe problem. Grease catches far faster on a cracked or displaced joint. That’s often why a kitchen sink keeps blocking however often it’s cleared.
5. A blockage in the main drain. If the sink gurgles when the dishwasher or washing machine empties, or the outside gully rises, the problem is past the kitchen.

Safe fixes to try first

• Run hot tap water for a few minutes. On a slow sink this can soften and move light grease.
• Plunge it properly. On a double sink, put the plug in the other bowl or hold a wet cloth over it, otherwise the plunger just pushes water out the other side. Cover the overflow too, then a dozen firm plunges.
• Clean the trap under the sink. Put a bucket underneath, unscrew the trap by hand, empty it and refit it carefully so it doesn’t leak. Only do this if you’re comfortable with it.
• Check the dishwasher filter if the sink backs up when the dishwasher drains.
• Look at the outside gully near the kitchen. If it’s full or overflowing, stop using water inside — the main drain is blocked.

What not to do

• Don’t pour fat or oil down the sink, even with hot water behind it. Let it cool, then wipe it out with paper towel and bin it.
• Skip caustic and chemical drain cleaners. They can damage pipes and trap seals, they’re dangerous if they splash out of a sink you’re plunging, and they leave the line hazardous for whoever clears it next.
• Don’t pour boiling water into a blocked sink. With nowhere to go, it sits in the sink and can soften PVC fittings and the trap seal.
• Don’t keep running the dishwasher into a blocked sink.

When it’s time to call a plumber

• It’s still slow after plunging and cleaning the trap
• It keeps blocking every few weeks or months
• Other fixtures gurgle when the sink drains, or the gully rises
• Water is leaking from under the sink
• There’s a sewer smell from the sink or outside

How Zebra finds and fixes it

Clear it properly, not just a hole through it. The hydro jetter scours the grease off the pipe walls instead of punching a small hole that closes up again in a few weeks. Where grease has hardened, the chain knocker breaks it up first.

Camera when it keeps coming back. A sink that blocks repeatedly gets the CCTV camera, and you watch the screen with the plumber. If grease is collecting at a crack, a displaced joint or a flat section of pipe, you’ll see it.

One fixed price, approved before any work starts. We quote one fixed price and nothing starts until you approve it. The quote is obligation-free.

The honest bit: jetting a sound pipe is a long-term fix. Jetting a damaged one buys time. Where the camera shows the pipe itself is the problem, the lasting fix is repairing that section, and you’ll see why on screen before you decide. Our workmanship is backed by a lifetime labour warranty. More on our blocked sinks and showers service.

Whose drain is it?

Everything on your side of the connection point is yours to maintain: the pipes under the house and yard, the overflow relief gully, and — in older suburbs — the boundary trap. Your water corporation (Yarra Valley Water, South East Water or Greater Western Water, depending on where you live) owns the sewer main itself, and the council owns the street's stormwater drains. Older and subdivided blocks sometimes share one combined drain across several properties, and a fault in the shared section is usually a shared cost. We camera and locate the fault first, so you know exactly whose side it sits on before anything is quoted — and if it turns out to be on the corporation's side, we'll say so and point you to their faults line rather than charge you for someone else's pipe. One tip worth acting on today: keep your overflow relief gully (the grated drain outside, usually near a side or rear wall) clear and uncovered. It's designed to spill outside instead of through your bathroom floor, and insurers can take a dim view of a blocked or built-over gully after a sewage spill.

Common questions

More plain-English help in our drain guides.