The water used to disappear immediately.
Then it started draining a little slower.
Now you've brushed your teeth, washed your hands or emptied the washing-up bowl and there's a pool of water sitting in the sink refusing to go anywhere.
Your first instinct might be:
Pour the strongest drain cleaner you can find down it.
But that's not necessarily the best place to start.
Many ordinary sink blockages are caused by material accumulating close to the sink itself. In some cases, you can clear the problem without specialist equipment.
The important thing is to work logically.
Start with the simplest possibilities, avoid creating a bigger problem and recognise when the blockage may be further into the drainage system.
Step 1: Work Out Whether It's Just One Sink
Before taking anything apart, look at the bigger picture.
Is only one sink draining slowly?
Or are several fixtures affected?
Try nearby sinks, baths or showers where appropriate.
If one basin is slow while everything else drains normally, the blockage may be relatively local.
If several fixtures suddenly have drainage problems, water is backing up elsewhere or toilets are behaving unusually, the problem could be further along the drainage system.
That's a different situation from a little hair caught beneath a bathroom plug.
Step 2: Check the Plug and Waste Opening
Start where you can actually see.
Bathroom basins commonly collect:
Hair.
Soap residue.
Toothpaste.
And general debris around the waste.
Kitchen sinks can accumulate food residue and grease.
If the plug or removable waste components can be safely lifted out according to their design, inspect the area immediately underneath.
You may discover the blockage before you've even opened the toolbox.
Remove accessible debris carefully and clean the components before testing the sink again.
Never force a component that doesn't appear designed to be removed that way.
Step 3: Remove Standing Water if Necessary
If the sink is completely full, working on it becomes much more awkward.
Remove some of the standing water into a suitable container before continuing.
This is particularly useful if you're eventually going to work beneath the sink.
Otherwise, the moment you disconnect something, you may discover exactly how much water the basin and pipework were holding.
Keep a bucket and old towels nearby.
They're considerably more useful before the spill than afterwards.
Step 4: Try Hot Water Where Appropriate
For some kitchen sink restrictions caused by ordinary grease or soap residue, hot water may help loosen deposits.
But this isn't a universal solution.
You need to consider the sink, pipework and what may have caused the blockage.
Don't assume that pouring boiling water into every type of sink or drainage system is automatically appropriate.
And don't keep adding water to a completely blocked sink that's already close to overflowing.
If simple flushing doesn't improve things, move on rather than repeatedly filling the basin.
Step 5: Use a Plunger Properly
A basic sink plunger can be surprisingly effective.
But there's more to it than aggressively bouncing it against the plughole.
The plunger needs to form a useful seal around the waste opening.
If the sink has an overflow, that can allow pressure to escape, so it may need to be appropriately covered while plunging.
There should normally be enough water around the plunger cup to help create the seal.
Then use controlled plunging movements.
You're trying to move the obstruction using pressure—not punish the sink.
After several attempts, test the drainage.
If the water suddenly disappears freely, you may have cleared it.
Step 6: Be Careful With Chemical Drain Cleaners
This deserves its own section because chemical products are often treated as the automatic answer to every blocked sink.
They aren't.
Different drain-cleaning products contain different substances and have specific safety instructions, limitations and compatibility considerations.
If you choose to use one, follow the manufacturer's instructions exactly.
Don't casually mix different cleaning chemicals.
And don't assume:
“If one dose didn't work, three times as much will.”
There's another practical consideration.
If strong chemicals have already been poured into a blocked drain and you later dismantle the pipework—or a plumber has to work on it—the trapped liquid may still contain those chemicals.
If you call a plumber after using a chemical product, tell them what was used.
Step 7: Check the Trap Under the Sink
If accessible debris and plunging haven't worked, the next potential blockage point is the trap.
The trap is the curved section of pipework beneath the sink that retains water and helps prevent drainage-system smells entering the room.
Its shape also makes it a convenient place for debris to collect.
Depending on the installation, some traps can be dismantled for cleaning.
Before touching it:
Place a bucket underneath.
Protect the surrounding cupboard or floor.
Take a photo of the arrangement if useful.
And make sure you understand how the components fit together.
When the trap is opened, expect water.
That's normal.
Step 8: Clean the Trap
If you can safely remove the appropriate section, inspect it.
You may find:
Grease.
Food debris.
Hair.
Soap residue.
Or a combination you'd rather not examine too closely.
Clean the trap thoroughly without damaging seals or components.
While it's disconnected, you can also determine whether the obstruction appears to be inside the trap itself or whether the problem may continue further into the waste pipe.
Avoid pushing unknown objects deeper into the drainage system.
Turning a nearby blockage into a more distant blockage isn't progress.
Step 9: Reassemble Everything Carefully
Once the trap is clean, put it back together correctly.
Make sure seals and washers are positioned as intended.
Connections should be secure, but that doesn't mean every plastic fitting needs to be tightened with as much force as physically possible.
Overtightening can damage components or seals.
Once reassembled, don't immediately fill the sink to the top.
Test it gradually.
Run a small amount of water while looking underneath.
Check every connection you've disturbed.
If everything remains dry, increase the flow and test the drainage properly.
Step 10: Check for Leaks Again
The sink drains beautifully.
Job done?
Almost.
Dry the pipework and surrounding area so that any fresh moisture is easy to spot.
Run the tap again.
Look around the trap joints.
Then check once more after the sink has held and released some water.
A tiny leak beneath a sink can go unnoticed inside a cupboard and eventually damage:
Cabinetry.
Flooring.
Decorations below.
Or surrounding materials.
Don't solve a blockage and accidentally create a leak.
What If the Sink Is Still Blocked?
At this point, you've learned something useful.
If the visible waste is clear and the trap is clean but water still isn't draining properly, the obstruction may be further into the waste pipe or drainage system.
That's when repeatedly dismantling random components becomes less useful.
Specialist drain-cleaning equipment may be required depending on the location and nature of the blockage.
A plumber or drainage professional can investigate further.
What About Drain Snakes?
Small manual drain-cleaning tools can be useful for certain local obstructions, particularly hair in appropriate waste systems.
But they need to be used sensibly.
Don't aggressively force a tool into pipework when you don't know:
Where the pipe runs.
What fittings are ahead.
What material the pipework is made from.
Or what you're actually trying to remove.
Professional drain-cleaning equipment can go considerably beyond the little plastic hair-removal tools sold for household use.
Know the difference.
Kitchen and Bathroom Blockages Aren't Always the Same
The likely material causing the blockage often differs.
In a bathroom
Common contributors include hair, soap residue and other products accumulating around the waste and trap.
In a kitchen
Grease, fats, food debris and detergent residue can contribute to restrictions.
Prevention therefore differs too.
A hair catcher can be useful in some bathroom fixtures.
In the kitchen, avoiding sending inappropriate food waste, fats and oils down the sink can reduce the amount accumulating in the drainage system.
The drain shouldn't be treated as an invisible rubbish bin.
Don't Keep Clearing the Same Blockage Forever
If the sink blocks once after years of normal use, clearing accumulated debris may solve the problem.
If it blocks again next week...
And again the month after...
Something else may be going on.
Repeated drainage problems can justify further investigation.
Possible issues can include persistent build-up, poor pipe arrangement, inadequate fall, damaged pipework or a blockage further along the system.
The exact cause needs to be established rather than assumed.
Repeatedly clearing the symptom isn't the same as fixing the reason it keeps happening.
Stop if Water Starts Appearing Somewhere Else
Pay attention to how the rest of the drainage system behaves while you're investigating.
If using one fixture causes water to appear in another, you hear significant gurgling elsewhere, multiple fixtures stop draining or wastewater begins backing up, the problem may extend beyond the individual sink.
At that point, treat it as a wider drainage issue.
Likewise, wastewater overflowing inside the property needs prompt attention.
When Should You Call a Plumber?
Consider getting professional help if:
The blockage keeps returning.
The trap is clear but the sink remains blocked.
Several fixtures are affected.
Water is backing up elsewhere.
The pipework is inaccessible.
You've discovered damaged or leaking pipes.
You don't feel comfortable dismantling the trap.
You suspect the blockage is further into the drainage system.
Or your attempts simply aren't working.
There's nothing wrong with trying sensible basic checks first.
The mistake is continuing to escalate DIY attempts after the evidence suggests the problem is no longer simple.
Prevention Is Easier Than Clearing It Again
Once everything is flowing properly, think about what probably caused the problem.
Use suitable strainers where helpful.
Remove hair before it disappears into the waste.
Don't pour cooking fats and oils down the kitchen sink.
Scrape food residue into the appropriate waste rather than washing it down the drain.
And pay attention when drainage begins slowing.
A sink often gives you some warning before it becomes completely blocked.
Water taking progressively longer to disappear is one of them.
Deal with the problem while the sink is slow, rather than waiting until it's holding an entire basin of dirty water.
Start Close to the Sink and Work Outwards
Blocked sinks can feel more complicated than they are because you can't see what's happening inside the pipe.
So use a simple process.
Check the visible waste.
Remove accessible debris.
Try appropriate basic clearing methods.
Inspect the trap if you're comfortable doing so.
Reassemble and check carefully for leaks.
Then reassess.
If the local components are clear and the problem remains, that's useful information in itself.
You've reached the point where further investigation may require someone with the right equipment.
A blocked sink doesn't always need an aggressive solution—start with the simplest possible cause, work methodically and know when the blockage has moved beyond a sensible DIY fix.