How to unblock a kitchen sink without calling a plumber

It's 7:30 AM. You're rinsing breakfast plates and the water's pooling around the drain, not going anywhere. The smell of last night's stir-fry is starting to rise. You've got 20 minutes before you need to leave.

By the end of this, you'll know exactly how to clear the blockage yourself, what tools to use, and when to stop trying and call someone in.

What's actually blocking your kitchen sink

Most kitchen sink blockages are grease. Cooking oil, butter, and fat from meat wash down the drain as liquid, then cool and solidify inside the pipe. Over weeks, that coating traps food scraps, coffee grounds, soap scum, and anything else that goes down.

In Sydney homes with older plumbing — cast iron or galvanised steel pipes — rust and scale buildup narrow the pipe diameter over time. A pipe that used to be 40mm across might be 25mm now. Doesn't take much to block it.

Less common but possible: a foreign object. A bottle cap, a small utensil, a chunk of something that shouldn't have gone down the disposal. If you have a garbage disposal unit, that's usually where these sit.

The blockage is almost always in one of three places: the drain basket itself, the P-trap directly under the sink, or the horizontal pipe between the P-trap and the wall. If it's further than that, you're into the building's waste stack, and that's a licensed plumber's job.

Try the plunger first

The cheapest tool that actually works. Not the toilet plunger — you want a flat-bottomed sink plunger, though in a pinch the toilet one will do if you clean it first.

Fill the sink with enough water to cover the plunger cup — about 5 to 8 centimetres. If you have a double sink, plug the other drain with a wet cloth or the stopper. You need to create a seal so the pressure goes down, not sideways.

Place the plunger over the drain. Push down slowly to expel air, then pull up sharply. Repeat 10 to 15 times. You're trying to dislodge the blockage with pressure, not shove it further down.

If the water starts draining, run hot water for two minutes to flush the loosened material through. If nothing happens after 15 plunges, move on.

Remove and clean the P-trap

The P-trap is the U-shaped pipe directly under the sink. It's designed to hold water and block sewer gases from coming up. It's also where most blockages sit.

You'll need a bucket, a wrench or pliers, and a torch if the space under your sink is dim. Place the bucket under the P-trap to catch water.

Most P-traps have two slip nuts — one where the trap connects to the sink tailpiece, one where it connects to the wall pipe. Loosen both by hand if you can. If they're tight, use a wrench. Turn anticlockwise.

Once the nuts are loose, pull the trap down and away. Water and whatever's blocking it will come out. Tip the contents into the bucket. If the blockage is a solid mass of grease and food scraps, that's your problem.

Rinse the trap in a separate sink or outside with a hose. Check the tailpiece and the wall pipe opening for debris. If they're clear, reattach the trap. Hand-tighten the slip nuts, then give them a quarter turn with the wrench. Don't overtighten — PVC cracks.

Run water. If it drains freely, you're done.

Use a drain snake if the blockage is deeper

If the P-trap was clean and the sink still won't drain, the blockage is further down the horizontal pipe or in the vertical stack. For this you need a drain snake — also called a plumber's auger. You can buy one at Bunnings for $15 to $40.

With the P-trap still removed, feed the snake into the wall pipe. Push it in slowly, turning the handle clockwise as you go. You'll feel resistance when the snake hits the blockage. Keep turning and pushing gently. The snake will either break up the blockage or hook onto it so you can pull it out.

Once you feel the resistance give way, pull the snake back out slowly. Reattach the P-trap and run hot water for three minutes to flush the pipe.

If the snake won't go more than a metre in, or if you hit something solid that won't move, stop. That's either a sharp bend in the pipe or a blockage in a shared stack. You're into plumber territory.

The Wenest take

In the homes we work in across the Inner West, the version of this that actually fails is when people keep pouring boiling water and bicarb down the drain for a week, convinced it'll work eventually. It won't. Grease blockages don't dissolve with heat once they've solidified in the pipe — they just soften slightly and re-harden. The fix is mechanical: plunger, trap removal, or snake. If those three don't work, the blockage is either in the building's stack or there's a structural issue with the pipe itself.

We've also seen people crack PVC traps by overtightening the slip nuts with a wrench. Hand-tight plus a quarter turn is enough. If it's leaking after that, the rubber washer inside the nut is probably worn and needs replacing — they're $2 at any hardware store.

When to stop and call a plumber

You should stop trying to fix it yourself if:

Water backs up into the other sink, the dishwasher, or another fixture when you run the tap. That means the blockage is in a shared pipe, not just your sink's drain.
You've removed the P-trap and snaked the pipe, and it still won't drain.
The sink has been slow-draining for weeks or months despite your attempts. That's a sign of scale buildup or a sagging pipe, not a simple blockage.
You're in a strata building and you suspect the blockage is in the common waste stack. You're not allowed to work on shared plumbing yourself, and your strata manager will need to coordinate access.
You don't have the tools, the space under the sink is cramped and you can't reach the trap, or you're just not comfortable doing it.

The cheapest quote is almost always the most expensive job. A licensed plumber will charge $180 to $280 plus GST for a standard call-out and blockage clear in Sydney. If they need to use a high-pressure jet or cut into the wall, that's $400 to $800. If you try to save $200 and crack a pipe in the process, you're looking at a much bigger bill.

This article is general guidance only. Any work involving cutting into pipes or accessing shared plumbing in a strata building must be performed by a licensed plumber — see NSW Fair Trading for licence verification.

Frequently asked questions

How long does it take to unblock a kitchen sink?

Most blockages clear in 10 to 30 minutes using a plunger or drain snake. If you've tried both methods for 20 minutes without progress, the blockage is likely deeper in the pipe or in the trap itself. At that point, you're looking at removing the P-trap or calling someone in.

Can I use Drano or chemical drain cleaner on my kitchen sink?

We've stopped recommending chemical drain cleaners for kitchen sinks. They rarely work on grease blockages, they can damage older PVC pipes, and if the blockage doesn't clear, you're left with caustic water sitting in the sink. Boiling water and a plunger are safer and just as effective for most clogs.

What causes kitchen sinks to block in Sydney homes?

Grease and cooking oil are the main culprits. They coat the inside of pipes and trap food scraps, coffee grounds, and soap residue. In older homes with cast iron or galvanised pipes, rust and scale buildup narrow the pipe diameter over time, making blockages more frequent.

When should I call a plumber instead of DIY?

Call a licensed plumber if water backs up into other fixtures when you run the sink, if you've removed the P-trap and the blockage is further down, or if the sink has been slow-draining for weeks despite your attempts. Also call if you're in a strata building and suspect the blockage is in a shared stack.

If you'd rather not be the one pulling apart pipes under the sink at 7 AM — that's literally why we exist. Wenest members get this handled without the calls. See how Wenest works.