How to Clean a Sink U-Bend: A Simple DIY Guide

A slow-draining or unpleasant-smelling sink is often caused by food, grease, hair or soap trapped inside the U-bend beneath it.

The U-bend—also called a trap—is designed to hold a small amount of water. This water creates a barrier that helps prevent drainage gases from entering your home. Its curved shape can also collect debris and eventually become blocked.

Cleaning an accessible plastic U-bend is a relatively straightforward DIY job, provided the fittings are in good condition and you work carefully.

How Do You Know If the U-Bend Is Blocked?

Common signs include:

• Water draining slowly from the sink
• Unpleasant smells from the plughole
• Gurgling noises
• Water remaining in the basin
• Small leaks around the U-bend fittings
• Debris returning through the plughole
• The sink becoming blocked again after surface cleaning

If several sinks, toilets or showers are affected simultaneously, the problem is unlikely to be limited to one U-bend.

What Collects Inside a U-Bend?

Kitchen traps commonly collect:

• Cooking fat and grease
• Food particles
• Coffee grounds
• Small pieces of packaging
• Soap residue

Bathroom traps may contain:

• Hair
• Soap
• Toothpaste
• Shaving products
• Small objects such as jewellery or bottle caps

A solid object should be retrieved carefully rather than pushed deeper into the pipe.

What You Will Need

Before starting, gather:

• Waterproof gloves
• A bucket or washing-up bowl
• Old towels
• A small cleaning brush
• Warm water
• Washing-up liquid
• A phone to photograph the pipe arrangement

Plastic compression fittings can usually be loosened by hand. Avoid using excessive force or gripping plastic fittings with metal tools, as this can crack or deform them.

How to Clean a Sink U-Bend

1. Stop using the sink

Turn off the taps and avoid using appliances that may empty into the same waste pipe, such as a dishwasher or washing machine.

Tell other people in the property not to use the sink while the pipe is disconnected.

2. Empty the cupboard

Remove cleaning products and stored items from underneath the sink. This gives you enough room to work and protects your belongings from dirty water.

3. Photograph the pipework

Take a clear photograph before loosening anything. This will help you remember:

• The direction of the U-bend
• How the pipes connect
• The position of the washers and seals
• How tightly the fittings originally sat

4. Position the bucket and towels

Place a bucket directly beneath the U-bend. Put towels underneath and around it to catch splashes.

Even when the sink is empty, the trap itself will contain water.

5. Loosen the fittings by hand

Support the U-bend with one hand while carefully turning the plastic compression nuts anticlockwise with the other.

Loosen each fitting gradually. If a fitting is seized, cracked, metal, corroded or difficult to reach, stop and contact a professional.

Do not force it.

6. Lower the U-bend into the bucket

Once the fittings are loose, carefully lower the trap and allow its contents to empty into the bucket.

Keep track of all washers and seals. Note their direction and position, as they must be refitted correctly.

7. Remove the blockage

Empty solid debris into a waste bag or bin.

Clean the inside of the U-bend using warm water, washing-up liquid and a suitable brush. Avoid pushing the blockage into another sink or drain.

Check for:

• Cracks
• Distortion
• Worn washers
• Damaged threads
• Hardened grease
• Objects lodged inside the trap

A damaged fitting should be replaced rather than reused.

8. Reassemble the pipework

Refit the washers and seals in their original positions. Align the pipework carefully and tighten the compression nuts evenly by hand.

The connections should be secure, but overtightening can damage plastic threads, seals or fittings.

Use the photograph you took earlier to confirm that everything is positioned correctly.

9. Test for leaks

Place dry tissue or kitchen roll around each connection. Run a small amount of water into the sink and watch the pipework carefully.

If everything remains dry, increase the flow slightly.

Check again after several minutes. A damp tissue will reveal a small leak that may not be immediately visible.

If a connection leaks:

1. Turn off the tap.
2. Place the bucket back underneath.
3. Check that the washer is correctly positioned.
4. Realign the fitting.
5. Tighten it gently by hand.
6. Test again.

Stop if the leak continues or the fitting appears damaged.

What If the U-Bend Is Clear?

If the trap is clean but the sink remains blocked, the obstruction may be located further along the waste pipe.

Possible causes include:

• Grease deeper inside the pipe
• A blockage in a shared waste pipe
• An incorrectly installed pipe
• Poor drainage fall
• A blockage in an outside drain
• Damaged underground drainage

Avoid inserting unsuitable tools or forcing objects beyond bends in the pipe.

Should You Use Chemical Drain Cleaner First?

Chemical cleaner can remain trapped inside the U-bend. Removing the pipe afterwards may expose your hands, skin or eyes to a concentrated chemical.

For this reason, avoid dismantling the trap if a strong chemical product has recently been used.

Never mix drain cleaners with bleach, acids, ammonia or other household products. Mixing chemicals can release dangerous fumes.

If chemical cleaner has already been added, tell the drainage professional before they begin work.

When Should You Avoid This DIY Job?

Contact a professional instead if:

• The fittings are metal or corroded
• The pipework is cracked
• A connection is already leaking
• The trap is difficult to access
• Chemical cleaner is present
• Several drains are affected
• Sewage is backing up
• The blockage repeatedly returns
• You are unsure how the seals fit
• The pipe cannot be reconnected securely

A small plumbing leak can damage a kitchen unit, floor or ceiling below, so do not continue if you are uncertain.

How Can You Prevent Future U-Bend Blockages?

You can reduce buildup by:

• Using a sink strainer
• Scraping plates before washing them
• Putting coffee grounds in the bin
• Never pouring cooking oil down the sink
• Removing hair from bathroom plugholes
• Cleaning sink stoppers regularly
• Investigating slow drainage early

Allow cooking fat to cool and dispose of it in a suitable container rather than washing it into the drainage system.

When Should You Call Better Drains?

If cleaning the U-bend does not restore normal drainage, the blockage may be deeper inside the waste or underground drainage pipe.

Better Drains can identify and clear difficult obstructions using professional drain-clearance and CCTV inspection equipment.

Contact our team if the sink remains blocked, several fixtures are affected or the problem repeatedly returns.

Frequently Asked Questions

Can I remove a plastic U-bend myself?

Many accessible plastic compression traps can be removed by hand. Stop if the fittings are seized, damaged, corroded or difficult to reach.

Why is there water inside the U-bend?

The trap intentionally holds water to prevent drainage gases from entering your home.

Why is my U-bend leaking after cleaning?

A washer may be incorrectly positioned, a pipe may be misaligned or a fitting may be too loose or overtightened. Damaged seals and fittings should be replaced.

Can I use a spanner on plastic fittings?

Plastic compression fittings are normally hand-tightened. Excessive pressure from a tool can crack or deform them.

Why is the sink still blocked after cleaning the trap?

The obstruction may be deeper inside the waste pipe or main drainage system and require professional equipment.