Quick answer
A bathroom sink that will not drain is usually clogged at the pop-up stopper, where hair and toothpaste collect, or in the P-trap under the sink. Pull and clean the stopper, clear the overflow hole, plunge with the overflow covered, then empty the trap into a bucket. If the trap is clean or other fixtures are slow too, the clog is inside the wall or in the branch drain. HomeServe puts drain cleaning at $100–$275. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed November 3, 2026· Next review May 2027
A bathroom sink drains slowly for two common reasons: the pop-up stopper has collected a plug of hair and toothpaste, or the P-trap under the sink is clogged. Both are reachable without opening a wall, and the stopper is the usual culprit.
Clear It in This Order
- 1Pull the stopper. Many lift straight out. Others are held by a horizontal rod behind the drain under the sink; unscrew the nut on that rod, pull the rod back, and the stopper comes up. Clean it and put it back.
- 2Clear the overflow. The small hole near the top of the bowl lets air in. If it is clogged, the sink drains slowly even with a clear pipe. Flush it with hot water and a bottle brush.
- 3Plunge it. Cover the overflow hole with a wet rag first, then use a small cup plunger over the drain.
- 4Clean the P-trap. Put a bucket under the curved pipe below the sink, loosen the two slip nuts by hand, and empty the trap. Check the gaskets are seated when you put it back, and run water to check for drips.
When the Problem Is Further Down
| What you notice | Likely cause |
|---|---|
| Trap is clean, sink is still slow | Clog in the drain pipe inside the wall |
| Sink and tub or shower are both slow | Clog in the shared branch drain |
| Several fixtures slow, toilets gurgle | Main line clog or blocked vent |
| Water under the cabinet after cleaning the trap | Gasket not seated, or a cracked trap; see leak under bathroom sink |
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
What to Skip
Chemical drain cleaners rarely dissolve a hair clog, can damage old metal drain pipe, and leave caustic water in the trap for whoever opens it next.
What a Repair Costs
HomeServe puts drain cleaning at $100 to $275. The drain cleaning page has the table and sources.
When to Call
Call when the stopper and the trap are clean and the sink is still slow, or when more than one fixture is affected. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
Reading to confirm what you already suspect?
Confirm it in two minutes instead — the pro on this line answers questions about YOUR situation all day: what it is, what it should cost, whether you even need service. If you want, they'll set the appointment on the same call.
No obligation to book
Frequently Asked Questions
Why is my bathroom sink draining slowly?
Usually hair and toothpaste caught on the pop-up stopper. Pull it out and clean it; if it is still slow, clean the P-trap under the sink.
Can a clogged overflow make a sink drain slowly?
YesThe overflow hole lets air in behind the draining water. If it is blocked, the sink can drain slowly even when the pipe is clear.
How much does it cost to fix a bathroom sink that won't drain?
HomeServe puts drain cleaning at $100–$275.
Sources
Methodology: How we source and verify data · Report an error
Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.