Skip the chemical drain cleaner and go mechanical first. Most household drains slow down because of a soft blockage — hair, soap scum, grease — sitting within the trap or the first metre of pipe, well within reach of a plunger, a drain snake, or the trap itself removed and cleaned. Chemical cleaners are hard on older pipes, do not work well on hair-based blockages, and make the job worse for whoever has to clear it mechanically if they fail.
Why drains slow down
Bathroom sinks and baths slow down mainly from hair combined with soap scum, which together form a surprisingly tough mat right at the point where the drain narrows into the trap. Kitchen sinks slow down mainly from grease, which is liquid when it goes down warm and solidifies as it cools further along the pipe, catching food particles as it does. In both cases the blockage is soft, close to the surface, and mechanically removable — it is not usually a hard mineral scale or a deep blockage requiring professional equipment.
Start mechanical, not chemical
Caustic drain cleaners generate heat that can damage older or plastic pipes, work poorly on hair-based blockages because they are formulated mainly for grease, and turn a straightforward mechanical clearance into a genuinely unpleasant and more hazardous job if the blockage does not clear on the first attempt. Start mechanical, and only consider an enzyme-based (non-caustic) cleaner as routine maintenance once the drain is already flowing freely.
How to clear it, step by step
- Clear standing water and remove visible debris
Bail out any water sitting in the sink or bath, and pull out anything visible from the plughole by hand — this alone sometimes solves it, particularly with bathroom hair blockages.
- Try a plunger first
Use a cup plunger for a flat sink or bath drain. Block any overflow opening with a wet cloth so the plunger builds pressure in the pipe rather than losing it through the overflow, add enough water to cover the plunger cup, and pump firmly ten to fifteen times before checking.
- Remove and clean the trap
The U-shaped trap under most sinks unscrews by hand or with light tool pressure. Put a bucket underneath first — it will be holding water. Empty it out, clear anything caught inside, rinse it, and reassemble hand-tight.
- Use a drain snake for anything further down
A flexible drain snake (also called an auger) reaches past the trap into the pipe run. Feed it in slowly, and when you meet resistance, turn the handle gently to catch the blockage rather than just pushing through it, then withdraw slowly.
- For a bath, check the overflow and pop-up assembly
Many bath drains have a pop-up stopper mechanism that accumulates hair around its linkage even when the visible plughole looks clear. Depending on the design, this usually lifts out for cleaning, or is accessed via the overflow plate.
- Flush with hot water
Once flow has improved, run hot (not boiling, especially on plastic pipework) water through for a minute or two to clear any remaining residue and confirm the drain is genuinely running freely, not just partially cleared.
For a kitchen sink slowed by grease, a kettle of hot (not boiling) water followed by a squirt of washing-up liquid, left for a few minutes before flushing with hot water, often shifts a grease-based blockage that a plunger struggles with because grease does not respond to pressure the way a soft hair mat does.
Keeping it from coming back
- Fit a simple hair-catching drain cover in the bath or shower — the single most effective prevention for bathroom drains.
- Never pour grease or cooking oil down a kitchen sink; let it cool and bin it instead.
- Run hot water through kitchen and bathroom drains briefly after use, particularly after anything greasy.
- Once flowing freely, an occasional enzyme-based drain treatment (not caustic) helps keep organic build-up from re-establishing.
When to call a plumber
Call a plumber if a plunger and drain snake both fail to restore flow, if multiple drains in the house are slow at the same time (which usually points at a blockage further down the shared line rather than an individual fixture), if water backs up from a different fixture when you run one — for example the bath gurgling when the toilet flushes — or if you have already used a chemical cleaner and it has not worked, since a plumber then needs to handle a pipe that may contain caustic residue.
Stop and call a qualified appliance technician or electrician if you find scorched or melted wiring, smell burning, see water that has reached electrical components, or if the fault returns immediately after a repair. Never bypass a safety device — thermal fuses, door interlocks and flood switches fail for a reason, and defeating one converts a broken appliance into a fire or flood risk.
