A blocked drain that simply will not clear is one of the most frustrating plumbing problems homeowners face. You pour drain unblocker down the sink, try plunging, maybe even use boiling water, yet the water still will not drain properly.

If your drain is not unblocking, there is usually a bigger issue deeper within the pipework that quick fixes cannot reach. In this guide, we will explain the most common reasons drains stay blocked, what actually works, and when it is time to call a drainage professional.

Why Your Drain Is Still Blocked

There are several reasons why your drain may refuse to clear, even after using drain unblockers or DIY methods.

1. The Blockage Is Too Deep In The Pipe

Most shop-bought drain unblockers only work on minor surface blockages.

If the blockage is deeper inside the drainage system, chemicals and plungers often cannot reach it properly. This is especially common with:

• Outside drains
• Kitchen sinks
• Toilets
• Shower drains
• Underground pipework

A deep blockage usually requires professional drain jetting or mechanical drain cleaning.

Fat, Grease & Food Build Up

One of the most common causes of blocked kitchen drains is grease buildup.

Cooking oils, fats, and food waste harden inside pipes over time, creating a thick blockage that water struggles to pass through.

Signs this may be the issue:

• Slow-draining water
• Bad smells from the sink
• Gurgling sounds
• Water backing up

Boiling water may temporarily improve flow, but severe grease buildup usually needs professional cleaning.

Hair & Soap Scum In Bathroom Drains

Bathroom sinks, showers, and baths often block due to:

• Hair
• Soap residue
• Toothpaste
• Shampoo build-up

Over time, this creates a thick clog that standard drain unblockers cannot fully dissolve.

This is why many people notice:

• Water pooling in the shower
• Slow-draining bathroom sinks
• Recurring blockages after “fixing” the problem

Tree Roots Or Collapsed Pipes

If none of the usual methods work, the issue may actually be structural.

Older drains can suffer from:

• Tree root intrusion
• Cracked pipes
• Collapsed drains
• Misaligned pipework

This is especially common in older properties across the UK.

In these cases, the blockage keeps returning because the drain itself is damaged.

Why Drain Unblocker Sometimes Does Not Work

Many people assume chemical drain unblockers will instantly solve the issue, but they are often ineffective against:

• Solid debris
• Deep blockages
• Heavy grease buildup
• Tree roots
• Compact hair clogs

Overusing chemical unblockers can also damage pipework over time and create safety hazards.

If you have already tried drain unblocker and nothing has changed, it is usually a sign the blockage needs professional equipment.

DIY Methods That Actually Help

Before calling a professional, there are a few things worth trying safely.

Hot Water & Washing Up Liquid

This can help break down grease inside kitchen pipes.

Plunger

A proper sink plunger can sometimes shift smaller blockages.

Drain Snake

Drain snakes are effective for hair clogs near the surface.

Remove The U-Bend

For kitchen sinks, blockages are often trapped in the U-bend beneath the sink.

Always place a bucket underneath first.

What NOT To Do

Avoid:

• Mixing chemical cleaners
• Using excessive force with rods
• Pouring bleach into blocked drains
• Ignoring recurring blockages

These can worsen the issue or damage the drainage system.

Signs You Need A Drainage Professional

You should contact a drainage specialist if:

• Water is completely backing up
• Multiple drains are blocked
• The blockage keeps returning
• Bad smells are getting worse
• Outside drains are overflowing
• DIY methods have failed

Professional drainage companies use:

• CCTV drain inspections
• High-pressure drain jetting
• Mechanical drain snakes
• Root cutting equipment

These methods fully remove the blockage instead of temporarily masking it.

How Professionals Unblock Drains Properly

Most professional drain cleaning services follow this process:

1. Drain Inspection

The drain is checked to identify the exact blockage location.

2. Drain Cleaning

High-pressure water jetting or specialist equipment removes the obstruction.

3. CCTV Survey

If needed, cameras inspect the pipes for damage or recurring issues.

4. Repair Recommendations

If the drain is damaged, repairs can then be recommended.

How To Prevent Drains Blocking Again

You can reduce future blockages by:

• Avoiding pouring grease down sinks
• Using drain covers in showers
• Regularly flushing drains with hot water
• Not flushing wipes or sanitary products
• Cleaning outdoor drains regularly

Small maintenance habits make a huge difference long term.

Final Thoughts

If your drain is not unblocking, there is usually a reason beyond a simple surface clog. While DIY methods can sometimes help, persistent or recurring blockages often point to deeper drainage problems that require professional equipment.

The sooner the issue is dealt with properly, the less chance there is of expensive pipe damage, flooding, or emergency plumbing callouts later on.