Drain unblocking is the process of removing whatever is stopping water from flowing freely through a pipe — usually with rods, high-pressure jetting, or a combination of the two. Most blockages clear once the obstruction is broken up or pushed through, and the underlying cause is identified so it doesn't simply happen again. Knowing the type of drain involved and the likely cause helps you judge whether it's a quick job or one that needs proper equipment.
What blocks a drain in the first place
Blockages rarely appear from nowhere. They build up gradually as material catches on a rough joint, a slight dip in the pipe, or an existing partial obstruction. Once water flow slows, more debris settles, and the blockage grows.
The usual culprits depend on which drain you're dealing with:
- Fat, oil and grease — poured down kitchen sinks, these cool and harden, narrowing the pipe over time.
- Wet wipes and sanitary items — these don't break down like toilet paper and snag easily, even ones labelled "flushable".
- Hair and soap scum — a common cause in bath, shower and basin wastes.
- Food waste — coffee grounds, rice and pasta swell or clump and sit in the pipe.
- Tree roots — fine roots work into joints in below-ground drains seeking moisture, then expand.
- Collapsed or displaced pipes — older clay or pitch-fibre pipes can crack or sag, trapping debris.
Wipes and fat together are a particularly stubborn combination, forming the congealed masses sometimes called fatbergs in larger sewers.
Internal waste versus below-ground drainage
Drain unblocking is the process of removing whatever is stopping water from flowing freely through a pipe — usually with rods, high-pressure jetting, or a combination of the two.
It helps to know where your problem actually sits, because the two are treated differently. Internal waste pipes carry water from a single appliance — the basin, bath, sink or washing machine — to the main stack. These are narrow, often 32mm to 50mm, and a blockage here usually affects just one fixture.
The soil pipe is the larger vertical pipe (the stack) that takes waste from toilets and connects everything to the drains below ground. A blockage in or below the soil pipe tends to affect several fixtures at once — for example, the toilet backing up when the washing machine drains.
Below-ground drains run from the house to either the public sewer or, in some properties, a septic tank or cesspit. These are wider, typically 100mm or more, and accessed through inspection chambers (the manhole covers in the garden or path). A blockage here can cause waste to surface at a chamber or drain slowly across the whole property.
Responsibility matters too. Drains within your boundary are generally yours to maintain, while shared lateral drains and public sewers are usually the water company's. If you're unsure where a blockage lies, checking which fixtures are affected and lifting the nearest inspection chamber often narrows it down.
Rodding, jetting and when each suits
The two main clearing methods work in different ways, and each has its place.
Rodding uses flexible rods screwed together and pushed along the drain by hand, sometimes with a corkscrew or plunger head on the end. It's mechanical and direct — good for breaking up a solid blockage or clearing roots in an accessible drain. Rodding is cheaper and simpler, but it mainly punches through an obstruction rather than cleaning the whole pipe wall.
Drain jetting uses water at high pressure through a specialised hose, with a nozzle that fires jets forwards and backwards. The forward jets cut through the blockage; the rear jets pull the hose along and scour the pipe as it goes. Jetting clears fat, scale and silt from the full circumference of the pipe, leaving it close to its original bore. It needs proper equipment and is more expensive, but it's far more thorough.
As a rough guide: a single blocked basin or a toilet that won't clear with a plunger may only need rodding or a hand auger. A recurring or widespread blockage, or a build-up of grease across a long run, usually responds better to jetting. A surveyor or drainage engineer will often jet a below-ground drain and then inspect it, rather than assume the blockage is fully gone.
When a CCTV survey is worth it
A CCTV drain survey sends a small waterproof camera along the pipe on a flexible rod, sending live footage back to a screen. It shows the inside of the drain in detail and pinpoints the exact location and nature of a problem.
A survey isn't needed for a straightforward one-off blockage that clears easily. It earns its cost when:
- A blockage keeps coming back in the same place, suggesting a structural fault rather than ordinary debris.
- You suspect root ingress, a collapse, or a displaced joint.
- You're buying a property and want to know the condition of the drains before committing.
- An insurance claim or a dispute over a shared drain needs documented evidence.
- Work is planned nearby and you need to map where the drains run.
The footage is usually recorded, and a written report may grade any defects. That record is useful if repairs follow, because it shows precisely what needs doing and where to dig — avoiding guesswork and unnecessary excavation.
Habits that keep drains clear
Most blockages are preventable with a few simple routines. Prevention is far cheaper than repeated clearing.
- Scrape plates and pans into the bin, and never pour fat or cooking oil down the sink — let it set and bin it.
- Flush only the three Ps: pee, poo and (toilet) paper. Wipes, cotton buds and sanitary items go in the bin.
- Fit a strainer over kitchen and shower plugholes to catch food scraps and hair.
- Run hot water through the kitchen sink after washing up to help carry grease away before it cools.
- Lift and check garden inspection chambers occasionally so you spot slow drainage early.
- If you have trees near the drain run, be alert to recurring slow drainage, which can signal early root ingress.
A drain that's draining slowly is giving you warning. Acting on it early — clearing the build-up before it solidifies — usually means a minor job rather than an emergency later.