5 Common Reasons Why Your Bathroom Sink Is Not Draining Properly

We’ve all been there — standing over the bathroom sink, waiting impatiently for the water to drain, only to watch it pool slowly or not go down at all. It’s not just frustrating; it’s a clear indication that something is wrong with your plumbing.

In this blog, we’ll break down five common reasons why your bathroom sink is not draining correctly, what signs to look out for, and how to fix or prevent them.

Looking for a trusted provider of bathroom plumbing services in London? Maintracts Services plumbers are here to help. Contact us on 020 8682 2244 or email info@maintracts.co.uk today for expert plumbing support.

The 5 Common Reasons Your Bathroom Sink Is Not Draining

1. Hair And Soap Scum Build-Up

The Culprit Behind Most Blockages

One of the most common sink blockage issues we see is hair. Combined with soap scum, toothpaste, and skincare residue, it creates the perfect sticky mess that clings to the inside of your pipes. Over time, this build-up restricts flow, leading to slow drainage or complete blockage.

Signs of a blocked bathroom drain from hair and soap scum include:

• Water is taking ages to drain
• Foul smells from the plughole
• A gurgling sound as the water struggles to pass through

DIY bathroom sink unblocking tips: Remove the plug and use a hair removal tool or tweezers to gently pull out debris. Flush with hot (not boiling) water and washing-up liquid. Avoid chemical cleaners, as they can corrode older pipes.

2. Buildup Of Bathroom Products

Everyday Items Causing Hidden Blockages

From shaving foam and moisturisers to toothpaste and facial scrubs, our daily routine leaves behind more than just a clean face. These residues can cling to pipe walls and contribute to a blocked bathroom sink drain over time, especially if the sink is not flushed properly.

Worse yet, some beauty products contain oils and waxes that solidify in colder pipes, resulting in bathroom drainage issues.

To reduce buildup:

• Rinse with hot water after using the sink
• Don’t rinse thick or oily products straight down the drain
• Fit a filter to catch excess debris

If you're facing persistent bathroom plumbing issues, it's time to investigate further or contact us.

3. Blocked Sink Trap (U-bend)

The Hidden Curve That Often Gets Overlooked

The U or P shaped bend under your sink — known as the trap — holds a small amount of water to prevent bad smells from the drain. But it’s also where debris like hair, toothpaste, and grime can collect and form a blocked bathroom sink.

This is a frequent cause when your bathroom sink is not draining despite clearing the surface.

DIY sink unblocking (if you’re confident):
Turn off the water supply, place a bowl underneath, and carefully remove the trap. Clear any debris and rinse the pipe before refitting.

If you're unsure or have an older system, it's best to consult a professional — learn more in our guide to DIY vs. Professional Plumbing.

4. Venting Or Airflow Issues

When Your Sink Gurgles Like It’s Talking Back

Your plumbing system needs air to function correctly. If the vent pipe (which lets air in and odours out) is blocked, the vacuum created can stop water from flowing freely. This can lead to gurgling sink noises, slow drainage, and water rising in one fixture when another is used.

This type of bathroom plumbing issue isn’t always visible and might need a plumber to inspect your system. Poor airflow could also signal broader drainage issues in your home.

This is particularly common in older properties across London. If you’re hearing odd noises from your drains, it’s time to check in with our experts.

5. Deeper Drain Blockages Or Pipe Damage

The Problems You Can’t See — But Shouldn’t Ignore

If none of the above resolves the issue, the blockage could be further down the pipework or even outside your property. Tree roots, broken pipes, or dislodged joints can prevent water from flowing, causing water to back up into the sink or overflow.

This often presents as:

• Water is not draining properly, even after unblocking
• Recurring blockages within days
• Unusual smells from nearby drains

In these cases, it’s crucial to know when to call a plumber for sink blockages. Where necessary, we have camera inspection tools to identify issues deep in the drain without tearing up your flooring.

For persistent issues, read more on the cost of plumbing repairs and what to expect when hiring a professional.

How To Prevent Bathroom Sink Blockage

Prevention is always better than a cure. Here’s how you can protect your sink from common issues:

• Install a filter or hair catcher over the plughole
• Run hot water for 20–30 seconds after every use
• Avoid disposing of thick lotions or wax-based products down the sink
• Regularly check under the sink for leaks or signs of damage
• Get a professional bathroom plumbing service in London for routine maintenance

Our experts can conduct thorough system checks and guide bathroom sink maintenance for long-term peace of mind.

Conclusion

If your bathroom sink is not draining, the cause could be anything from hair blockage and soap scum to a blocked trap or more serious drainage problems. The good news? Most minor issues can be fixed quickly with a bit of DIY. But if you’ve tried it all and still find water standing still, it’s time to call in the pros.

We’ve been keeping London’s homes running smoothly for over 40 years, offering reliable, certified plumbing solutions backed by real expertise. Whether it’s a hidden water leak or a blocked drain, you can trust us to resolve the issue swiftly.

Contact Maintracts Services on 020 8682 2244 or email info@maintracts.co.uk to request your quote today.

Ready to get started? Contact us now and speak with a plumbing expert near you.

FAQs

1. Why is my bathroom sink draining slowly?

Slow drainage is often due to a buildup of hair, soap, and debris in the pipes or trap. It may also indicate issues with venting or deeper blockages in the system.

2. What causes a complete blockage in the bathroom sink?

Complete blockages typically occur when debris, such as hair, oils, and toothpaste, accumulates over time, eventually forming a solid barrier in the pipes.

3. Can I fix a blocked sink myself?

Yes, minor DIY bathroom sink unblocking tips include removing hair from the drain, using a plunger, or cleaning the trap. For persistent issues, professional help is often the best solution.

4. Is it safe to use chemical drain cleaners?

We don’t recommend it. Harsh chemicals can damage your pipes and pose a health risk. Use natural solutions or contact a plumber instead.

5. Why does water back up when I use the sink?

This is often a sign of a blockage or poor drainage further down the pipe. It may also indicate air venting problems within the system.

6. How often should I clean my bathroom sink drain?

A quick monthly clean with hot water and washing-up liquid can prevent most blockages. Consider a quarterly check of the trap.

7. When should I call a plumber for a blocked sink?

If DIY methods don’t work, or the problem returns frequently, it’s time to call a plumber. They can inspect deeper drainage problems.

8. Can blocked bathroom sinks cause other plumbing issues?

Yes. Persistent blockages can lead to leaks, pipe damage, or backflow, which can affect nearby drains and fixtures.