A drain that has stopped is one of the few household problems that gets worse by the hour. For a UK homeowner facing a blocked drain, the useful questions in the first ten minutes are narrow: is anything backing up into the house, where is the blockage, and is it even your drain to fix?
Most blockages are within a few metres of the property, are caused by fat, wipes or root ingress, and can be cleared with rods or a hired jetter. The ones that cannot are the ones worth spending money to diagnose properly, because repeated call-outs on a drain with a structural defect are money spent on the same problem over and over.
First: stop it getting worse
Before anything else:
Stop running water into the system. No washing machine, no dishwasher, no baths, minimal flushing. Every litre you add has to go somewhere.
Lift the inspection chamber covers and look. This tells you almost everything about where the blockage sits.
If waste water is entering the house, treat it as an emergency and a health risk. Keep people and pets away from it, and call a drainage engineer.
Do not reach into a chamber or attempt to enter one. Confined spaces and foul water are dangerous, not just unpleasant.
Reading the chambers
Work from the house outwards. Lift each cover in turn.
First chamber full, later ones empty - the blockage is between those two points, and it is on your property.
All chambers full, including the last one before the boundary - the blockage is downstream, possibly in a shared drain or the public sewer.
All chambers empty but the house is backing up - the blockage is inside, between the appliance and the first chamber.
That single exercise tells you where to point the effort and, often, who is responsible for paying.
Who is responsible for a blocked drain
This is the question that saves people the most money, and a surprising number of homeowners pay for work their water company would have done.
In England and Wales, the general position since the transfer of private sewers is that the water and sewerage company is responsible for the public sewer and for lateral drains - broadly, the sections of pipe beyond your property boundary that carry waste away, including some shared runs. The homeowner is responsible for the drains within their own boundary that serve only their property. Shared drainage serving more than one property often falls to the water company.
Scotland and Northern Ireland operate under different arrangements, and the detail matters, so check with your own water authority rather than relying on a general summary.
The practical rule: if the blockage is beyond your boundary, or in a run shared with neighbours, call your water company before you call anyone else. They will usually attend and clear it at no cost to you. If it is within your boundary and serves only your house, it is yours.
Call the water company first, always. The worst outcome is that they attend, confirm it is your side of the line, and you are exactly where you started - minus nothing. The best outcome is that they clear it for free. A drainage firm attending an emergency has no incentive to raise the question for you.
What you can safely clear yourself
Sink and basin blockages
Usually a trap or a short run of waste pipe. Clear the trap by hand into a bucket, check the waste pipe, and use hot water and detergent rather than caustic chemicals. Chemical drain unblockers are hard on older pipework, hazardous to handle, and create a serious splash risk for whoever opens the pipe afterwards. If you do use one, tell the engineer.
Toilet blockages
A plunger or a toilet auger clears most. The common cause is wipes, and no wipe is truly flushable regardless of the packaging.
Outside gully blockages
Rodding an accessible run
Enter at the chamber closest to the blockage, always turning the rods clockwise so they do not unscrew and leave a section in the pipe. Work gently. Forcing rods into a pipe you cannot see can damage a fragile clay run.
Where to stop
Stop and call an engineer if:
Rodding does not clear it within a reasonable effort.
The blockage recurs within weeks.
You can see broken pipe, standing water in the chamber base that never clears, or root growth.
Waste is backing up into the house.
What a drainage engineer does and what it costs
High pressure jetting clears fat, scale and root ingress properly rather than punching a hole through it. Typically a few hundred pounds for a routine visit, more out of hours.
A CCTV drain survey puts a camera through the run and produces a report with a location and depth for any defect. Often in the region of £150 to £400 depending on the length surveyed and whether a report is included.
Patch lining or excavation and repair where a section has collapsed or dropped. This is where costs move into the thousands, particularly under a driveway or extension.
Two things worth insisting on. Ask for the CCTV footage and the written report, not just a verbal summary - it is your evidence for an insurance claim or a future sale. And ask whether the blockage was a cause or a symptom: a drain that blocks twice a year has a defect, and jetting it annually is renting a solution.
Prevention that actually works
Fat, oil and grease go in the bin, not the sink. Wipe pans before washing.
Clear gullies seasonally, especially in autumn.
Know where your inspection chambers are, and keep them accessible rather than paving or decking over them.
What to do in the next 30 minutes
Stop using water in the house.
Lift every inspection chamber cover and note which are full and which are empty.
Work out from that whether the blockage is inside your boundary.
Call your water company if there is any chance it is theirs.
Clear the outside gully by hand, because it is often that.
Photograph the chambers, full or empty, before anyone touches anything.
Drainage is the one part of the house you cannot see, so the paperwork is the map. Home+ gives you a free place to keep the CCTV survey, the drain layout, and every jetting invoice against the property, so the next engineer starts with information rather than guesswork - and so a buyer’s surveyor gets a straight answer. Record drainage work in Home+ as soon as the job is done.
FAQ
Who is responsible for a blocked drain in the UK? Broadly, you are responsible for drains within your boundary that serve only your home, and the water company is responsible for the public sewer and lateral drains beyond the boundary, including many shared runs. Arrangements differ across the UK nations, so check with your own water authority - and call them before calling a private firm.
How much does it cost to unblock a drain? A routine jetting visit commonly runs to a few hundred pounds, with out-of-hours call-outs costing more. A CCTV survey is often £150 to £400. Repairs involving excavation run into the thousands.
Why does my drain keep blocking in the same place? Repeated blockages in one spot almost always mean a defect - a dropped joint, a partial collapse, root ingress or a badly laid section. A CCTV survey will find it. Repeat jetting will not fix it.
Does home insurance cover blocked drains? Buildings policies sometimes include cover for damage caused by escaping water and occasionally for drain repairs, and some include a home emergency add-on covering call-outs. Routine clearance is usually excluded. Check your wording before you assume.
