How Much Does It Cost to Unblock an Outside Drain?

How much it costs to unblock an outside drain depends on where the blockage actually is. A blocked gully, the grated drain where a downpipe or kitchen waste pipe discharges, is usually a short job. A blockage in the underground pipe between inspection chambers needs rods or a jetting unit and takes longer. And if the blockage is in the public sewer, you should not be paying for it at all. Working out which of the three you have before you call is the best way to get an accurate price. Our standard rates by job type and time band are on the published rate card.

What decides the cost of unblocking an outside drain?

Three things: where the blockage is, what caused it, and when the work is done. Most price differences between two outside drain jobs come down to the first.

Location sets the method. A gully can often be cleared by hand and with a short rod. An underground run needs access from an inspection chamber, and a stubborn or long blockage needs a jetting unit. The further in and the harder to reach, the more time and equipment the job takes.

The cause sets how long it takes. Leaves and silt shift easily. Set fat from a kitchen, wet wipes, builders' sand or cement, and tree roots do not.

Timing sets the rate band. Our prices are split into standard hours (7am to 5pm), evenings (5pm to midnight) and night (midnight to 7am). An outside drain that is slow but not overflowing can often wait for a standard-hours slot, which is usually the cheapest choice.

A blocked gully is usually the shortest job

If water is pooling around the grate but your inspection chambers are clear, the blockage is almost certainly in the gully or its trap. That is normally the quickest outside drain to clear.

Gullies collect whatever runs off the roof and out of the kitchen: leaves, moss, grit and, below kitchen waste pipes, fat. The trap under the grate holds water to stop smells, and it is where debris settles. Clearing it usually means lifting the grate, scooping out the debris and rodding or jetting the short connection to the underground drain.

A gully that blocks every autumn is a leaf problem, and a gully guard or clearer gutters will save more money than repeat visits. A gully below the kitchen that blocks every few months is a fat problem, and it will keep coming back until less fat goes down the sink.

Blocked inspection chamber or underground pipe

If an inspection chamber is full of standing water, the blockage is in the pipe leaving that chamber. That is a drain clearance job done from the chamber, and it takes more time and equipment than a gully.

The engineer will usually rod or jet from the full chamber towards the next one downstream. Most blockages of wipes, paper and fat clear this way in one visit. Our drain clearance service covers this kind of job, and a jet is used where rods will not shift it.

If the pipe clears but water drains slowly again, or the jet keeps hitting the same point, there is probably something wrong with the pipe itself: a displaced joint, a sunken section or roots. That is when a camera inspection earns its cost, because repeated clearance of a damaged pipe is money spent treating a symptom.

When the blockage is in the public sewer, not your drain

If your chamber is clear but the one downstream is full, or several neighbours have the same problem, the blockage is probably in a shared drain or public sewer. In London that is normally Thames Water's responsibility, and they clear it at no charge to you.

In England, most drains that serve more than one property, and pipes that run beyond your boundary, have been looked after by the water company since October 2011. The drain that serves only your property, within your boundary, is yours. A simple test is to lift each inspection chamber cover in turn, starting nearest the house. Your blockage sits between the last full chamber and the first empty one.

If that point is outside your boundary or in a shared section, report it to the water company before paying a private contractor. Our guide on who pays for a blocked drain in London explains the boundary rules, including terraces, flats and rented homes.

What pushes the price up

Hard blockages, damaged pipes and poor access are the usual reasons an outside drain costs more than a standard clearance. A good engineer should tell you which of these they have found before carrying on.

Set fat, cement or sand. Hardened fat and building materials need longer jetting, and cement sometimes needs cutting out with specialist heads.

Tree roots. Roots in a drain need cutting rather than jetting, and they grow back unless the joint they entered through is sealed.

No accessible chamber. If there is no inspection chamber, or it is buried under paving or decking, the engineer has to work from a gully or rodding eye, which is slower. Uncovering a buried chamber may be needed.

A damaged pipe. If the clearance reveals a crack or collapse, the repair is a separate job and should be quoted separately. It should not be added to the unblocking bill.

What you can safely check first

You can lift a gully grate and remove leaves and debris by hand, wearing gloves, and you can lift inspection chamber covers to see which ones are full. Both help and cost nothing.

Do not pour chemical drain cleaner into an outside drain. It rarely shifts a blockage in an underground pipe, and it leaves a hazard for whoever clears it afterwards. Do not climb into a chamber; lift the cover, look, and put it back securely. If water is rising towards the house or sewage is coming up through a gully, stop using the sinks, toilets and washing machine until the drain has been cleared.

How to compare quotes for an outside drain

Compare what each quote covers, not just the first figure. A low price that stops after the first half hour or excludes jetting is not cheaper if the blockage needs either.

Ask the same questions of everyone. Is the price fixed for clearing the blockage or charged by time? Is jetting included, or an extra? What happens if the blockage is in the sewer, not my drain? Is VAT included? Is there a separate charge for attending at this time of day? Is a camera check included, and if not, what does it add? Our breakdown of what drain jetting costs covers the jetting side of that in more detail.

If you want the price agreed before anyone travels, tell us which chambers are full, whether the gully is overflowing and whether neighbours are affected, and we will confirm which rate applies.

For how drain unblocking is priced more generally, see our guide to how much drain unblocking costs in London.