The Bathroom Sink Clog Is Always Hair, and It's Always Gross

Quick answer: Nine times out of ten, the clog is a wad of hair and soap scum hanging off the pop-up stopper, within six inches of the drain opening. Pull the stopper and clean it before you buy a single chemical.

What the box says

"Pour one capful down the drain. Wait 15 minutes. Flush with hot water. Enjoy free-flowing drains!"

Enjoy is a strong word for what's about to happen.

What you'll actually need

• A plastic barbed drain strip (the brand most stores carry is Zip-It), a few dollars. The single best tool in this whole job.
• A cup plunger, the flat kind, roughly $8 to $15. Not the toilet plunger with the flange. Keep those two separate forever.
• A bucket and an old towel for the cabinet floor.
• A flashlight, because the inside of a vanity is darker than a cave.
• Tongue-and-groove pliers (channel locks), roughly $15 to $25.
• A 1/4-inch hand auger (drain snake), roughly $15 to $30. You only need it if the easy stuff fails.
• A dedicated scrub brush. More on this later.
• Spare slip-joint washers, or a whole plastic P-trap kit, roughly $8 to $15. This is the drive-back part. Bathroom sinks take 1-1/4 inch. Kitchen sinks take 1-1/2 inch. The two sit side by side in the store, and you'll grab the wrong one with total confidence.

The steps

1. Find out if it's only this sink. Run water in the tub and flush the toilet. If they're slow or gurgling too, the problem is farther down the line, and the rest of this list won't touch it. Skip to the bottom. If it's only the sink, the clog is close, and you're about to win.

1. If someone already poured in a chemical drain cleaner, put on safety glasses and rubber gloves now. Don't plunge and don't open the trap while that water is sitting there. Caustic cleaner can splash into your eyes. Flush it out with plenty of cold water first if the sink will drain at all. If it won't, read the last section.

1. Pull the stopper. Some lift straight out or come free with a quarter turn. Most are held by a horizontal pivot rod under the sink, at the back of the drainpipe. Unscrew the nut on that rod by hand, slide the rod out an inch, and lift the stopper from above.

It'll come up wearing a gray, slimy wig. This is normal. You aren't the first person in your house to scream at it.

1. Clean the stopper, then run the plastic strip down the drain. Push it in, twist it, pull it out slowly. Repeat until it comes up clean.

Each pull brings up something worse than the last. Keep going. Courage.

1. Test it. Run hot water for a full minute. If it drains fast, put the stopper back with the pivot rod passing through the loop at the bottom of the stopper, tighten the nut by hand, and you're done. Most people stop right here.

1. Still slow? Plunge. Put a couple of inches of water in the basin. Stuff a wet rag tight into the overflow hole near the top of the sink, because otherwise all your pressure escapes through it. Seal the cup over the drain and give it 15 to 20 sharp strokes.

Skip the rag once and the overflow shoots a jet of drain water straight at your shirt. You'll only skip it once.

1. Pull the P-trap. That's the U-shaped pipe under the sink. Put the bucket directly beneath it. Loosen the two slip nuts by hand, counterclockwise as you look at them from the nut side. If they're stuck, wrap a rag around the pliers' jaws so you don't crack the plastic. Tip the trap into the bucket.

This is where the lost earring turns up, the one somebody in your house said went down the drain months ago. They were right. Admit it gracefully.

1. Clean the trap and snake the pipe into the wall. Scrub the trap out. Then feed the auger into the short horizontal pipe that disappears into the wall (the trap arm), crank it clockwise as it goes, and pull it back slowly.

Use a brush you bought for this. Grabbing the "old" toothbrush from the cup on the counter means learning, in a calm conversation that evening, that it wasn't old.

1. Reassemble and test hard. Each slip-joint washer has a tapered side. The taper faces toward the pipe it seals against, away from the nut. Hand-tighten, then a quarter turn more with pliers. No more on plastic. Fill the basin to the brim, pull the stopper, and run a dry paper towel around every joint while it drains.

A paper towel finds a drip your eyes swear isn't there.

Leave the vanity cleaner than you found it. Wipe the cabinet floor, toss the expired lotion that's been under there since the house was built, and put the bucket away rinsed. Whoever opens that door next will notice.

Where it goes wrong

It drips after you put it back. Usually a washer is in backward, sitting crooked, or cracked from being overtightened. Take that joint apart, seat the washer straight with the taper facing the right way, and snug it up. If the washer is flattened or split, replace it. This is exactly why you bought spares.

The stopper won't close, or won't open. The pivot rod missed the loop on the stopper and is just poking the side of it. Pull the rod, line it up with the flashlight, and try again. If it moves but doesn't seal, move the clip on the flat, holey strap (the clevis) up or down a hole until the lift knob works the stopper all the way.

It's still slow, even with a clean trap. The clog is past the trap arm, deeper in the wall. Run the auger farther. A sink that gurgles and drains sluggishly with no clog anywhere can also be a venting problem, and that's not a pliers job. The same trap-and-snake approach works on other drains in the house, covered step by step in Unclog a Drain With a Plunger, a Snake and Ten Minutes. The kitchen is its own animal, though. If the dishwasher's involved, start with Your Dishwasher Won't Drain. Do This Before You Call Anyone.

The old metal trap crumbles in your hand. Chrome traps rust thin from the inside, and old ones come apart at the first touch. Don't panic. Swap in a 1-1/4 inch plastic trap kit. It's cheaper, it won't corrode, and it takes about fifteen minutes.

When to call a pro

Call a licensed plumber if more than one fixture is slow or backing up, if water rises in the tub when you run the sink, or if you smell sewage. That points to the main line, and a 25-foot hand snake won't reach it.

Call one if the sink is full of chemical drain cleaner and won't drain at all. Tell them exactly which product went in. They'll want to know before they open anything.

Call one if the pipe inside the wall is cracked, corroded or loose, or if you suspect a venting problem. Work on drain lines and vents inside walls often needs a permit, and codes vary by area, so check with your local building department before you go hunting behind drywall.

Everything above that point is yours. And from now on, a drain-hair catcher on that sink runs a few dollars, which is a fair price for never meeting the stopper wig again.