A bathroom sink usually slows because hair, soap, and grooming residue collect around the stopper and trap. Location matters: if only that sink is affected, start with accessible parts; if other drains are slow too, suspect a shared restriction.
Clean the stopper and drain opening first
Remove the stopper according to the sink design and clear hair and residue around it. Many restrictions sit just below the drain flange and can be removed without opening plumbing or using chemicals.
Watch whether the basin drains slowly but steadily
A slow but steady drain often fits a partial local restriction. If water stops completely, backs up elsewhere, or a nearby toilet gurgles, the problem may be farther down the drainage system.
Do not mix chemical treatments with disassembly
If chemical drain cleaner has already been poured in, avoid opening the trap until you have followed the label precautions; corrosive liquid may remain trapped. For hair and soap, mechanical removal is usually more predictable.
Quick recurrence can indicate the trap or a shared line
If cleaning the stopper helps for only a few days, buildup may remain in the trap or wall pipe. A recurring slowdown combined with other affected fixtures deserves plumbing diagnosis rather than repeated chemical treatments.
Sources
- U.S. Environmental Protection Agency (EPA) — WaterSense Home Maintenance — Household water maintenance, leaks, fixtures, and efficiency.