Bathroom Sink Clogged: Common Causes and What to Do

Bathroom sinks block for a narrower set of reasons than kitchen sinks, and one cause accounts for most of them. The good news is that it usually sits within reach, a few inches below the drain opening.

The stopper is usually the answer

Most bathroom sinks have a pop up stopper operated by a lever behind the faucet. Underneath the sink, that lever connects to a horizontal rod which passes through the drain body and hooks into the bottom of the stopper.

That rod sits directly in the flow, and it is exactly the sort of obstruction hair wraps around. Over months it collects a dense mat of hair bound together with soap residue, and everything else that goes down catches on it.

The result is a sink that has slowed gradually rather than blocked suddenly. If that matches what you are seeing, start here.

Getting the stopper out

Some stoppers lift straight out. Try that first, and turn it as you lift, since many simply unhook with a quarter turn.

If it will not come, look underneath. You will find a small nut on the back of the drain body with the horizontal rod passing through it. Put a bowl under it, unscrew that nut by hand, and withdraw the rod. The stopper then lifts out freely.

Clean everything off it, wipe inside the drain body as far as you can reach, and reassemble. Push the rod fully back in before tightening the nut, or the stopper will not seal when you want to fill the sink.

Take a photo before dismantling anything if you are unsure how it goes back.

A drain snake, used gently

If the stopper comes out clean, a small hand snake or one of the barbed plastic strips sold for the purpose will reach further into the drain body and the start of the pipe.

Feed it in slowly and turn rather than push. The aim is to hook material and draw it back out. Driving it hard tends to compact the blockage instead.

What comes out is usually unpleasant and usually the whole problem.

Cover the overflow before plunging

Bathroom sinks have a small opening near the rim that stops them overfilling. It connects into the drain below the stopper.

Plunging without sealing it accomplishes very little, because the pressure simply travels up and out through that opening. Hold a damp cloth firmly over it, or have someone else do so, and plunge with a few inches of water in the sink.

This one detail is the difference between plunging a sink working and not working, and it is the step most often skipped.

The trap

If the stopper and the snake have not done it, the U bend underneath is next. Bucket first, then unscrew the collars by hand.

Check the horizontal section running into the wall as well as the bend itself. A trap that comes out clean while the sink still will not drain places the blockage beyond it, which changes what needs to happen next.

Soap residue, not just hair

Hair alone would mostly wash through. What makes it hold is the residue left by soaps and washing products, which coats the pipe and binds loose material into a mat.

That is why a bathroom sink used mainly for hand washing and shaving still blocks, and why the buildup returns on a predictable cycle once it has started. Clearing the visible mat helps. Clearing the coating it is stuck to is a different job.

What not to reach for

Chemical drain cleaner. A hair and soap mat around a stopper rod is a physical obstruction sitting inches from the opening. Removing it by hand takes a few minutes. Pouring caustic liquid onto it is slower, less reliable, and leaves that liquid in the sink if it does not work. Our note on drain cleaning approaches covers the trade offs.

Boiling water. Plastic waste pipe and seals do not appreciate it, and a sink blockage is rarely grease anyway, so there is little to gain.

Force on old fittings. Metal traps and drain bodies in older bathrooms can be corroded. If a fitting will not move by hand, stopping is usually cheaper than continuing.

When it is not just the sink

A sink that blocks on its own, while the tub, shower and toilet all behave, is a local problem. That is the ordinary case.

If the tub or shower is slow at the same time, if the toilet gurgles when the sink drains, or if water rises in one fixture when another is used, the restriction is in shared pipework. Our article on drains that keep clogging covers that pattern, and a gurgling toilet explains what the noise indicates.

When to ask for help

Sensible points to stop are a clean stopper and clean trap with no improvement, more than one fixture affected, fittings that will not come apart, any sign of a leak under the sink after reassembly, or a blockage that returns within weeks.

For drain work, see drain cleaning. For fixture problems, plumbing repair.

Frequently asked questions

Why does my bathroom sink drain slowly but not block?

That is the signature of buildup around the stopper rod. It narrows the opening rather than sealing it, so water still gets away, just slowly. It usually continues to worsen until the obstruction is removed.

Do I need to remove the stopper to clean the drain?

Usually yes, if you want to deal with the cause. The mat forms on and around the stopper mechanism itself, and poking past it without removing it tends to push material further in rather than take it out.

Why is my sink slow again after I cleaned it?

If it returns within weeks, the coating inside the pipe is probably still there, and it gives new material something to catch on. A quick return can also mean the restriction was always further down than the part you cleared.

For plumbing service in Houston, call (877) 563-1074 to connect with an independent plumbing service provider.