How to Unblock a Sink Without Harsh Chemicals
· 5 min read
The washing-up water is not going anywhere. It sits in the bowl with a grey film on top, and every few minutes it drops by a millimetre, as if to make a point. A bathroom basin gives the same warning in a different way, draining more slowly each morning until brushing your teeth feels like a small flood. Before reaching for a bottle of caustic cleaner, it is worth knowing that most household sink blockages sit within arm's reach and clear with simple tools.
What is usually causing it
Kitchen sinks and bathroom basins block for different reasons, which is useful, because the cause points to the fix.
- Kitchen sinks collect fat, oil and food scraps. Warm grease runs freely down the plughole, then cools and sticks to the inside of the pipe, catching rice, coffee grounds and crumbs as they pass.
- Bathroom basins gather hair, soap residue and toothpaste. Hair wraps around the pop-up plug mechanism and forms a mat that soap binds together.
- Both can suffer from small objects dropped by accident, and in hard-water areas a crust of scale narrows old pipes over time.
Before you start
Put on rubber gloves and clear the cupboard under the sink, since you may need to get at the pipework. Have a bucket, an old towel and a torch ready. If anyone has already poured a chemical drain cleaner into the sink, do not plunge or open the pipes: splashes can burn skin and eyes. Flush with plenty of cold water first, read the product label and, if the water still will not move, leave it to a professional rather than adding anything else. Never mix cleaning products, as some combinations release harmful fumes.
The order to try things in
- Clear the plughole. Lift out the strainer or pop-up plug. Many bathroom plugs twist out or unclip; some are held by a rod behind the tap that loosens with a small nut. Pull away any hair and gunk you can see. A bent wire hanger or a cheap plastic hair-catching strip reaches a few centimetres further.
- Try hot water. For a greasy kitchen sink, pour a kettle of hot, not boiling, water slowly into the plughole. It softens fat enough to shift a light blockage. Avoid boiling water on plastic pipework, ceramic basins that may crack under sudden heat, or a sink already full of standing water.
- Use a plunger. A small cup plunger made for sinks works better than a toilet plunger. Block the overflow hole with a damp cloth, or the second bowl of a double sink with its plug, so the pressure goes down the pipe instead of out of the overflow. Run a few centimetres of water to cover the cup, press it firmly over the plughole and pump up and down a dozen times before lifting it off sharply. Repeat several times before deciding it has not worked.
- Empty the trap. The U-shaped or bottle-shaped section under the sink is designed to catch debris. Put the bucket underneath, unscrew the plastic nuts by hand, and tip out the water and whatever came with it. Rinse the trap in another sink or outside, check the rubber seals are seated properly, and refit it hand-tight. Run the tap and look for drips.
- Reach further with a drain snake. If the trap was clear, the blockage is in the pipe beyond it. A flexible drain auger, fed in through the open pipe where the trap was, can hook or break up a plug of hair or grease. Turn the handle gently as you push and do not force it against resistance.
What about bicarbonate of soda and vinegar?
The fizzing mixture is popular because it feels like something is happening. It can freshen a smelly drain and help loosen a light film, but it is not strong enough to clear a solid blockage, and the foam has nowhere to go if the pipe is full of water. Treat it as maintenance rather than rescue: a spoonful of bicarbonate followed by a cup of vinegar, left for a while and then flushed with hot water, does no harm on a slow drain.
Quick reference
| What the sink is doing | Usual culprit | Start with |
|---|---|---|
| Basin drains slowly, gets worse each day | Hair around the plug | Remove and clean the plug |
| Kitchen sink full, water barely moves | Grease and food in the trap | Plunger, then empty the trap |
| Sink gurgles when another appliance drains | Partial blockage further along | Drain snake beyond the trap |
| Several sinks and the shower are slow together | Problem in a shared pipe or the drain outside | Call a plumber |
When it is not a job for you
Stop and call for help if water rises in more than one outlet at once, if dirty water appears in a sink when the toilet is flushed, if there is a sewage smell outdoors, or if a pipe joint is cracked or leaking. Those signs suggest the trouble lies in a shared waste pipe or the drain beyond the house, where a camera and proper jetting equipment are needed. The way professionals track down and clear deeper blockages is described in the piece on a commercial plumber's response to blocked drains.
Keeping the sink clear afterwards
- Wipe greasy pans with kitchen roll before washing them, and let cooking fat set in a container for the bin.
- Keep a strainer in the kitchen plughole and empty it into the food waste.
- Pull hair from the basin plug every week or two, before it builds into a mat.
- Run hot water for a little while after washing up to carry residue through the trap.
- In warm weather, do not leave a slow drain with standing water; damp, food-rich pipes draw insects, as the advice on preparing a home for summer pests points out.
Scale on old fittings narrows the flow too, and the same mild acids that work on taps help around the plughole; the steps are in removing limescale from taps, kettles and showers. If a sink keeps blocking however careful you are, the pipework itself may be poorly laid, which is worth fixing properly when the room is next updated, as the guide to a bathroom renovation on a budget suggests.
