Blocked Drains, Drain Cleaning and Repairs in the UK
A blocked toilet, an overflowing outside drain and a sewer that keeps backing up are not all the same problem. The useful starting point is to work out how far the water is getting and whether the trouble is local to one fitting, one property or a longer drainage run.

What is happening?
Outside drain overflowing
If the gully is filling from below, the restriction is usually downstream of it rather than in the short waste pipe above.
Work through the likely causesToilet keeps blocking
One toilet behaving badly points somewhere different from several toilets and gullies backing up together.
See what the pattern suggestsSeveral drains affected
When several fittings stop draining at once, look farther along the system and check whether neighbouring properties are affected.
Narrow down the locationSame blockage keeps returning
Repeated clearing may only be removing the symptom if roots, a displaced joint or heavy deposits are catching solids in the same place.
Why blockages recurSuspected broken drain
A crack, open joint and complete collapse are different defects and do not call for the same repair.
Understand the repair optionsNeed a CCTV survey
A camera becomes far more useful once the pipe is clean enough for its wall and joints to be seen properly.
What a survey can showClearing the blockage is only one part of the job
Rods or high-pressure water can restore the flow through many ordinary blockages. That does not by itself establish why the pipe blocked. If the same section fails repeatedly, a camera survey may show whether deposits were left behind or whether paper and solids are catching on roots, a displaced joint, deformation or another defect.
Equally, a single blockage after inappropriate material has gone down the drain is not evidence that the underground pipe needs lining or excavation.
Responsibility depends on the drainage layout and where in the UK the property is located. If several properties are affected, check with the relevant sewerage provider before assuming the blocked section is yours.
Useful starting points
What it cleans well, and what it cannot repair.
Why root cutting may restore flow without sealing the point of entry.
How the remaining pipe shape and access affect the choice.