If the basin holds standing water that won’t drain at all, the culprit is almost always a wad of hair and soap scum caught on the pop-up stopper — the plug that lifts and drops when you pull the lever behind the faucet. That’s where hair snags first, and it’s the fix that works most often. Pull the stopper, clean it, and the water usually rushes out. If it doesn’t, the clog has moved down into the P-trap or the branch drain, and you escalate from there. Skip the chemical drain cleaner — it rarely clears a full stoppage and makes every step after it more dangerous. Here’s the whole job, start to finish, with no bottle of caustic gel involved.
Note: this guide is for a sink that’s fully clogged with standing water. If yours still drains but just crawls, you don’t need the full teardown — start with our shorter fix for a slow-draining bathroom sink instead.
Likely causes, ranked
Work this list top to bottom. Nine times out of ten you’ll solve it at the first row.
| Cause | How to tell | Fix |
|---|---|---|
| Hair & soap scum on the pop-up stopper | Water sits or barely moves; you pull a slimy black wad off the stopper | Remove and clean the stopper |
| Clog packed in the P-trap | Stopper is clean but water still won’t drain; other fixtures are fine | Plunge, then unscrew and clean the trap |
| Clog past the trap in the branch drain | Trap is clear but the drain backs up again; sometimes a nearby drain gurgles | Hand-snake the branch line through the trap arm |
How to unclog it, step by step
Put on gloves and set a bucket under the trap before you start. Do the steps in order — most sinks clear by step 1 or 2.
- Remove and clean the pop-up stopper. Try lifting or twisting the stopper straight out first — some pull free. If it won’t budge, it’s held by the pivot rod. Clear everything out from under the sink, look behind the drain tailpiece, and find the horizontal metal rod running into the pipe, held by a plastic or metal retaining nut. Loosen that nut by hand or with channel-lock pliers, work the pivot rod back and pull it out of the tailpiece, then lift the stopper straight up out of the basin. Pluck the hair off it, scrub it with an old toothbrush, and rinse. This alone fixes the majority of clogged bathroom sinks.
- Fish the drain with a Zip-It tool. With the stopper out, push a barbed plastic hair-clog tool (Zip-It) down the drain opening, twist, and pull. Drag out whatever it grabs. Repeat until it comes back clean.
- Plunge it — and seal the overflow first. This is the step people get wrong. Stuff a wet rag firmly into the overflow hole near the top rim of the basin. If you skip this, your plunging pressure blows straight out the overflow instead of down the pipe. Reinsert the stopper or set a flat cup plunger over the drain, add enough water to cover the plunger cup, and pump hard a dozen times. Break the seal to check if it drains.
- Remove and clean the P-trap. Still blocked? The U-shaped pipe under the sink — the P-trap — catches debris by design. Keep the bucket under it, unscrew the two slip nuts by hand (or with pliers), and drop the trap. Expect standing water and gunk to pour out. Clean it, poke out any packed hair, and check the rubber slip washers while it’s apart — cracked or flattened washers cause drips on reassembly, so replace them if they look tired. If you find your trap was already dripping, see our guide to fixing a leaking bathroom sink trap. Reassemble hand-tight plus a light nudge with pliers.
- Hand-snake the branch drain. If the trap was clear but the sink still backs up, the clog is downstream in the branch line. Feed a small hand auger (drum snake) into the trap arm — the pipe heading into the wall — crank it in, catch the blockage, and pull it back out. Run hot water to flush. The same method works on a kitchen line too; here’s how to unclog a kitchen sink if that’s your next project.
One rule throughout: no chemical drain cleaner. It rarely clears a full stoppage — it only bores a small hole — and the heat it generates can soften and warp PVC and corrode older metal pipes. Worse, if you plunge a sink that’s holding caustic cleaner, that liquid can splash back onto your skin and eyes. On a septic system it also kills the bacteria the tank relies on. Mechanical clearing, done above, is safer and actually works.
Tools & parts you’ll need
- Zip-It or barbed hair-clog tool
- Flat cup plunger
- Channel-lock (tongue-and-groove) pliers
- Bucket and rags
- Replacement P-trap slip washers
- Small hand auger / drum snake (only if you reach the branch-drain step)
- Rubber gloves
DIY cost vs. calling a pro
This is one of the cheapest plumbing jobs to do yourself, since the tools are inexpensive and reusable.
| DIY | Licensed plumber | |
|---|---|---|
| Typical cost | $0–$40 (mostly tools you keep) | $125–$350 to clear the drain |
| What you pay for | Zip-It ~$5, cup plunger ~$10, trap washers ~$3; snake ~$20–$30 if needed | Labor, minimum service call, and snaking the line |
Prices are typical US ranges for 2026 and vary by region and after-hours rates.
Difficulty & time
Easy to moderate — most people clear it in 20 to 45 minutes with basic hand tools; add time only if you get to the P-trap teardown or snaking.
When to call a licensed plumber
- The clog returns fast even after you cleaned the stopper and trap
- Several fixtures back up at once, or a drain gurgles when another runs — that points to the main line
- You hit corroded or seized metal trap nuts you can’t loosen without risking a crack
- Sewage smell or water backing up into other drains
- You already poured chemical drain cleaner in — tell the plumber so they can protect themselves
FAQ
Why is my bathroom sink completely clogged with standing water?
Almost always a hair-and-soap-scum wad on the pop-up stopper, where hair snags first. Pull and clean the stopper before anything else — it’s the most common fix.
Do I really have to plug the overflow hole to plunge a sink?
Yes. The overflow opening near the top rim connects to the drain. If you don’t stuff a wet rag into it, your plunging pressure escapes there instead of forcing down against the clog.
Can I use baking soda and vinegar instead?
It can help with light odors and grease film, but it won’t push through a solid hair clog blocking a full sink. Mechanical removal — cleaning the stopper, fishing with a Zip-It, plunging, or pulling the trap — is what actually clears standing-water clogs.
What if my stopper won’t lift out?
It’s held by the pivot rod. Reach behind the drain tailpiece under the sink, loosen the retaining nut on the horizontal rod, slide the rod out, and the stopper lifts free. Reverse the steps to reinstall.
Is it safe to run the disposal or use chemicals to help?
A bathroom sink has no disposal, and you should skip chemical drain cleaner: it seldom clears a full clog, its heat can warp PVC, and it can splash back on you when you plunge. Stick to the mechanical steps above.
More on why caustic cleaners are a poor first move: see the U.S. EPA’s guidance on household hazardous waste, which lists drain cleaners among the corrosive products to handle with care.