How to Unblock a Sink With a Plunger

A plunger clears a blocked sink by shoving a column of water back and forth through the trap until the clog breaks apart, and the two things that decide whether it works are a sealed overflow and enough water in the bowl to cover the cup. Get those right and most kitchen and basin blockages give way in under a minute of steady pumping. Get them wrong and you can plunge for ten minutes with nothing to show for it.

Use the right plunger for a sink

There are two common shapes and they are not interchangeable. A cup plunger is a plain rubber dome on a stick, and its flat rim is designed to sit on the flat porcelain or steel around a sink drain. A flange plunger has a soft rubber sleeve that folds down out of the cup, and that sleeve exists to push into the curved throat of a toilet.

If a flange plunger is all you have, tuck the flange up inside the cup so the rim goes flat again. It will work, just not as well as a proper cup plunger. What will not work is a small novelty sink plunger with a rim narrower than the drain fitting, because it cannot bridge the metal waste flange to reach flat surface.

Before you plunge, clear the decks

Two minutes of prep saves a lot of futile pumping.

• Scoop out standing water until roughly 50mm to 75mm is left. You want enough to submerge the cup, not so much that it slops over the edge on the first stroke.
• Lift out the plug, strainer or pop-up waste. Hair and grease often sit right under the strainer and pull straight out with a bent piece of wire, which saves you plunging at all.
• If you poured caustic drain cleaner down earlier, do not plunge. That liquid is still sitting in the trap and plunging will splash it back at your face. Flush it through with plenty of cold water first, or leave the job for a plumber.
• Smear a thin ring of petroleum jelly around the plunger rim if the rubber is old and stiff. It makes a real difference to the seal.

Block the overflow, or nothing happens

This is the step most people skip and it is the single biggest reason plunging fails. Bathroom basins and most kitchen sinks have an overflow slot, either a small opening near the rim of the basin or a hidden channel behind the waste fitting. When you push down on the plunger, pressure escapes straight up through that channel instead of travelling along the pipe toward the blockage.

Press a damp cloth firmly into the overflow opening and hold it there, or get someone else to. On a double bowl kitchen sink you also need to block the second drain, because the two bowls share a waste pipe and pressure will simply push through to the other side. A wet cloth stuffed into the second plughole and weighted with your hand does the job.

The plunging technique that actually shifts a clog

Set the cup over the drain at an angle so one edge touches first, then lower it flat to squeeze the trapped air out sideways. You should feel it suck down slightly.

Now push down slowly for the first stroke. A hard first push just breaks the seal and sprays water up your arms. Once you feel resistance, keep the rim planted and pump with short sharp strokes, roughly 15 to 20 of them over about 20 seconds. Keep the cup on the drain the whole time. The pull stroke matters as much as the push, because dragging the clog back toward you loosens it from the pipe wall in a way that pushing alone will not.

On the last stroke, yank the plunger clean off the drain. If the water disappears with a gurgle, you are through. If it drops slowly, plunge again. Three or four rounds of 20 seconds is a fair effort. Beyond that you are unlikely to get anywhere and it is time for a different approach.

Finishing off

Once it drains, run the hot tap hard for two or three minutes. What you have usually done is punch a hole through a grease and hair plug rather than remove it, so the remaining material is still clinging to the pipe wall waiting to catch the next thing that comes past. A long flush of hot water carries loosened debris out to the main drain and buys you months instead of days.

Rinse and dry the plunger properly. Rubber left damp in a cupboard goes tacky and cracks around the rim, and a cracked rim will never seal again.

When plunging is the wrong tool

Plunging works on soft blockages within a metre or so of the drain, which covers the majority of kitchen and basin problems. It is the wrong tool in a few situations.

1. Nothing moves after four proper attempts. The blockage is either solid or further down the pipe than pressure will reach. Move to a drain snake, or undo the trap under the sink with a bucket beneath it and clear it by hand.
2. Every drain in the house is slow. That points at the shared soil stack or the drain run outside, not at your sink. Plunging one fixture will not touch it.
3. Water backs up into another appliance when you plunge, such as the washing machine standpipe filling up. Stop, because you are pushing waste sideways into somewhere it should not go.
4. You can see or smell chemical cleaner sitting in the bowl. Deal with that first.

A cheap plunger and a wet cloth clear an awful lot of sinks. Keep one under the kitchen sink and one in the bathroom, because carrying the same plunger between a toilet and a food prep area is not something you want to be doing.