1. What is drain unblocking?

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A drainage system normally works because wastewater can flow freely through the pipe:

House → drain → sewer → treatment works

A blockage interrupts that flow:

House → drain → 🚫 blockage

Water may then:

• Drain slowly.

• Stop draining completely.

• Back up into a sink, bath or shower.

• Cause a toilet to flush poorly.

• Come back through an outside drain.

• Produce foul smells.

• Eventually overflow from an inspection chamber or manhole.

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A drainage engineer's job is essentially to locate the blockage, determine what is causing it, remove it, and check that the pipe is flowing properly afterwards.

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2. What types of blockages are there?

There are several very different types, and this is important because the correct equipment depends on the blockage.

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🟢 Fat, oil and grease (FOG)

Extremely common in kitchen drainage.

Cooking fats, oils and grease can stick to the inside of pipes.

Over time:

small deposits → narrowing → severe restriction → complete blockage

The pipe can eventually look almost like a tiny tunnel through a thick layer of grease.

This is usually treated with high-pressure water jetting.

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🟢 Food and organic material

Things such as:

• Food scraps

• Coffee grounds

• Rice

• Flour

• Vegetable matter

can accumulate, particularly in kitchen drains.

Grease often makes the problem worse because organic material sticks to it.

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🟢 Wet wipes and sanitary products

These are particularly problematic in toilet drainage.

Even products marketed as "flushable" can contribute to blockages because they don't break down in the same way as toilet paper.

Common offenders include:

• Wet wipes

• Sanitary towels

• Nappies

• Cotton buds

• Paper towels

• Excessive toilet paper

These may form a large tangled mass.

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🟢 Hair

Hair is particularly common in:

• Showers

• Baths

• Bathroom sinks

Hair can combine with soap, shampoo residue and grease to create a surprisingly solid obstruction.

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🟢 Tree roots

This is a completely different category.

Roots can enter through:

• Cracked pipes

• Open joints

• Displaced joints

• Defective connections

Once inside, they continue growing.

You can therefore get:

small crack → root enters → root grows → debris catches → blockage

Root ingress is especially relevant to older clay drainage systems.

A jetting machine can remove the immediate roots, but it doesn't necessarily solve the underlying structural problem.

That's where CCTV becomes important.

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🟠 Silt, mud and soil

External drains can accumulate:

• Silt

• Sand

• Soil

• Leaves

• Small stones

This is particularly common in surface-water drainage.

If enough material accumulates, the pipe's capacity progressively decreases.

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🟠 Scale and mineral deposits

Hard-water areas can develop mineral deposits inside pipes.

The internal diameter gradually decreases:

100 mm pipe → deposits → much smaller effective opening

This can cause chronic slow drainage.

Mechanical descaling or specialist water jetting equipment may be required.

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🔴 Collapsed or broken pipe

This is technically not simply a blockage.

Imagine:

──────────────

Normal pipe.

Then:

──────╲╱────

A section has collapsed.

You can remove whatever material is sitting there, but the water still won't flow properly because the pipe itself has failed.

This requires repair or replacement.

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🔴 Displaced joints

Older pipes can move or settle.

For example:

Pipe A → | ← Pipe B

The joint no longer lines up correctly.

Waste can catch on the edge and create repeated blockages.

Again, cleaning the blockage doesn't necessarily solve the underlying problem.

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🔴 Foreign objects

Engineers can occasionally find surprisingly strange things in drainage systems:

• Toys

• Building materials

• Stones

• Timber

• Plastic

• Clothing

• Sanitary products

These often require mechanical removal rather than simply flushing them away.

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3. How do engineers unblock drains?

There isn't one universal machine.

A professional drainage company has several methods.

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Method 1 — Drain rods

This is one of the simplest techniques.

Sections of flexible/rigid rods are connected together and pushed into the drain.

They're useful for:

• Relatively accessible blockages

• Soft obstructions

• Initial investigation

They're inexpensive and straightforward.

But there's an important distinction:

Rodding doesn't necessarily clean the pipe.

It may simply create a hole through the blockage.

So water starts flowing again, but material can remain stuck to the pipe walls.

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4. High-pressure water jetting

This is one of the most important pieces of professional drain equipment.

A powerful pump forces water through a hose fitted with a specialised nozzle.

The nozzle has jets pointing backwards and/or forwards.

The backwards jets:

• Propel the hose through the pipe.

• Break material away.

• Wash debris back toward the access point.

The forwards jet helps penetrate the blockage.

Depending on the equipment, the system can produce very substantial water pressure.

It's particularly effective against:

• Grease

• Mud

• Silt

• Organic deposits

• Some root growth

• General accumulated debris

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5. Different jetting nozzles do different jobs

This is something people often don't realise.

A professional doesn't necessarily use the same nozzle for everything.

For example:

Standard/fan nozzle

Good for general cleaning.

Penetrating nozzle

Designed to concentrate water and break through a blockage.

Root-cutting nozzle

Used with specialist equipment to attack root growth.

Grease-cutting nozzle

Designed to help remove heavy grease deposits.

Descaling equipment

Used where mineral deposits have built up.

So when someone says:

"We'll jet the drain."

the actual effectiveness depends partly on what nozzle and pressure/flow combination they're using.

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6. Mechanical drain machines

These use rotating cables or cutting heads.

They're particularly useful when something needs to be physically broken or cut apart.

For example:

• Hard deposits

• Roots

• Tough obstructions

• Certain foreign objects

Think of it somewhat like a powered flexible drill/cutting system travelling through the pipe.

However, careless mechanical work can potentially damage an already fragile pipe, so the engineer needs to understand the condition of the pipe.

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7. CCTV drain camera

Strictly speaking, CCTV isn't an unblocking machine.

It's an investigation tool.

But it's extremely important because it tells the engineer:

"Why did this blockage happen?"

The camera can reveal:

• Roots

• Cracks

• Collapsed pipe

• Displaced joints

• Grease deposits

• Foreign objects

• Standing water

• Poor gradients

• Failed connections

This is the difference between:

"We got your drain flowing again."

and:

"We discovered why it keeps blocking."

The second is much more valuable when you have recurring problems.

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8. Vacuum tanker

For larger drainage systems, a vacuum tanker may be used.

It's essentially a very powerful suction system mounted on a vehicle.

It can remove:

• Silt

• Sludge

• Sewage

• Mud

• Large quantities of debris

These are particularly useful for:

• Large chambers

• Commercial sites

• Sewage systems

• Culverts

• Deep drainage infrastructure

A domestic blockage normally wouldn't require one.

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9. Plumbing plungers

At the household level, the simplest equipment is often a plunger.

It uses pressure changes to move an obstruction.

Useful for:

• Toilets

• Sinks

• Baths

It can be surprisingly effective for a small local blockage.

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10. Chemical drain cleaners

These are products containing chemicals designed to break down certain organic materials.

I'd be cautious about relying on them.

They can sometimes help with minor household blockages, but they don't solve structural problems, and they can be dangerous to people and equipment.

If a drainage engineer subsequently needs to work on the pipe, residual chemicals can also create a safety issue.

For a persistent blockage, mechanical or water-based investigation is generally more informative.

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11. A professional engineer may use several pieces of equipment together

For example, imagine your outside inspection chamber is full of water.

The engineer might do:

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Step 1 — Inspection

Open the chamber and establish where the water is coming from.

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Step 2 — Rodding

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Attempt to establish a temporary flow.

Step 3 — Jetting

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Thoroughly clean the pipe.

Step 4 — CCTV

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Put a camera through the pipe.

Step 5 — Diagnose

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Discover:

"There is root ingress at approximately 9 metres."

Step 6 — Repair recommendation

Rather than repeatedly unblocking the drain, recommend:

root treatment / patch repair / relining / excavation, depending on the actual condition.

That's a much better approach than simply returning every few months to unblock the same pipe.

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12. There's an important distinction: blockage vs structural failure

This is probably the most useful thing to remember.

Blockage

The pipe is intact, but something is obstructing it.

Example:

Grease has accumulated inside the pipe.

Solution: clean/remove it.

Structural defect

The pipe itself is defective.

Example:

A clay pipe has cracked and roots are entering.

Solution: repair the pipe.

If you repeatedly unblock a structurally defective drain without fixing the underlying problem, you're effectively treating the symptom rather than the disease.

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13. How this relates to your inspection chamber

Going back to your earlier question, suppose you have:

House → inspection chamber → sewer

and the inspection chamber keeps filling.

An engineer shouldn't simply say:

"We'll jet it."

They should establish where the blockage is.

For example:

Blockage upstream of chamber

House → 🚫 → chamber → sewer

Your private drainage is blocked.

Blockage downstream

House → chamber → 🚫 → sewer

The problem may be further along the private/shared/public sewer.

Structural problem

House → chamber → cracked/blocked pipe → sewer

The blockage may keep returning until the defective section is repaired.

This is why knowing which side of the inspection chamber the problem is on can be extremely useful.

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14. And this is particularly relevant to rats

There's an interesting connection to your earlier question.

A drain that is:

• partially blocked,

• damaged,

• full of food/grease,

• connected to the sewer,

• and accessible to rodents

can create an attractive environment for rats.

But you generally don't want to solve a rat problem simply by installing a flap without understanding the drainage.

Ideally:

CCTV → understand the drainage → unblock/clean → repair defects → install appropriate rat protection

if required.

That gives you a much more robust solution.

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The equipment in one table

EquipmentMain purpose

Drain rodsPush through simple blockages

PlungerSmall household blockages

High-pressure jetterClean/remove grease, silt and debris

Root-cutting equipmentRemove intrusive roots

Mechanical cable/cutterBreak/cut tough obstructions

CCTV cameraFind the cause and location of defects

Vacuum tankerRemove large quantities of sludge/debris

Locator/sondeLocate the camera/pipe underground

Descaling equipmentRemove hard mineral deposits

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The key principle

A good drainage engineer shouldn't just aim for:

"The water is flowing again."

They should aim for:

"The water is flowing, we know why it blocked, and we've established whether the pipe itself is healthy."

For a property you're considering buying, CCTV after unblocking is particularly valuable because you can distinguish a one-off blockage from a drainage system that's fundamentally defective.