A bathroom sink that drains slowly is almost never a plumbing problem inside the walls. It is hair, soap residue and toothpaste built up somewhere in the first metre of pipe, and most of that is reachable without a wrench, working through three levels of intervention before anything gets taken apart.
Start with the stopper
Most bathroom sinks have a pop-up stopper controlled by a pivot rod under the sink, and it is the single most common place hair collects.
- Look under the sink for the pivot rod running from the drain pipe back to the stopper linkage.
- Twist and lift the stopper, or loosen the pivot rod first if it will not lift on its own.
- Pull the stopper fully out and check the base of it for a wrapped mat of hair and soap scum, which is very often the entire blockage.
- Clean it off completely, rinse it, and drop it back into place before testing the drain.
A plunger works on sinks too
If clearing the stopper does not fix it, a small cup plunger works on a sink the same way it works on a toilet, using trapped water pressure to push the clog free.
- Block the overflow hole near the top of the basin with a wet cloth, held firmly, so the plunger builds pressure in the drain instead of just pushing air out through the overflow.
- Add enough water to the basin to cover the plunger cup.
- Set the plunger squarely over the drain and give it a dozen firm, steady plunges rather than short sharp ones.
- Remove the plunger on an upstroke and check whether the water drains freely.
A drain snake or a bent wire hanger
For a clog further down than the stopper or a plunger reaches, an inexpensive hand-crank drain snake, or in a pinch a straightened wire coat hanger with a small hook bent into the end, fed down through the drain opening will usually hook and pull out the hair clump causing the blockage. Turn it gently rather than forcing it, and pull slowly so whatever it catches comes out with it instead of being pushed further down the pipe. Work it in a few centimetres at a time, turning as you go, until you feel it hook onto something solid rather than just sliding through water.
Why chemical drain cleaner is a last resort
Caustic drain cleaners can damage older metal pipes and the rubber seals in a P-trap, and if the clog does not fully clear, that chemical is now sitting in standing water the next time someone opens the trap to fix it properly by hand, which is a genuine safety concern for whoever does that work next. Mechanical clearing, plunging or snaking, deals with the actual blockage rather than trying to dissolve it, and it is the safer first move on any bathroom sink, especially in an older home where the pipes underneath may not be as new as the fixtures above them.
If the clog is below the trap, the pipes are original to the house, or the slow drain keeps coming back within weeks, call our plumbing and electrical fixture team serving Kitchener, Waterloo and Cambridge rather than keep working chemical cleaner through ageing pipework.