Blocked Outside Drains, Gullies & Manholes

In short: Outside drains block when leaves, silt, fat, wipes or tree roots collect in a gully, a manhole chamber or the underground pipe between them. Clearing them rarely means digging: rods and high-pressure jetting reach the blockage from the nearest manhole. If an outside drain is shared with neighbours, the water company may be responsible rather than you.

Most homes have more outside drainage than people realise. There's usually a gully by the kitchen wall where the sink waste and a downpipe empty, one or more manhole covers marking where pipes join, and an underground run carrying everything to the public sewer under the road. A problem anywhere along that route shows up outside first, as a gully that won't empty or a manhole lid with water seeping round it.

Because the pipes are hidden, the skill is in working out where the blockage sits before trying to clear it.

Foul drains and surface water drains

Many properties have two separate systems. Foul drains carry waste from toilets, sinks, baths and appliances. Surface water drains carry rain from roofs, yards and driveways, often to a soakaway or a separate sewer. Older houses commonly have a combined system where both go into the same pipe. Knowing which you have matters: a blocked surface water drain is mostly a nuisance in heavy rain, while a blocked foul drain means waste water has nowhere to go.

Common causes of outside drain blockages

Leaves, moss and silt washed off roofs and patios into gullies
Fat from the kitchen sink setting in the gully and the first stretch of pipe
Roots entering through old clay pipe joints, especially near trees and hedges
A sunken or broken section where the ground has moved, often under driveways
Wipes and nappies from toilets collecting at the first manhole

What you can check yourself

Pull any visible leaves or debris off the gully grid and scoop out what you can reach, wearing gloves. Then lift your manhole covers, starting nearest the house. A full chamber means the blockage is further downstream; an empty one means it's between that point and the house. That information alone saves time when you call. Don't climb into a chamber, and don't try to force rods through a pipe that won't take them, as this can push the blockage tighter or break an old joint.

How we clear outside drains

We work from the manholes, rodding or jetting the run between the chamber that's full and the one that's empty. Jetting is particularly good outside because it scours silt and grease off the pipe walls rather than just punching a hole through. On a run that has blocked before, or where we find root or pipe debris coming back with the water, we put a camera through to check the condition of the pipe.

Who is responsible for an outside drain?

If the drain serves only your home and is inside your boundary, it's normally yours. Where your drain joins a neighbour's, or runs under a neighbour's garden or the pavement, it's normally the water company's responsibility. Road gullies on the street belong to the local council. See who pays for a blocked drain for the full explanation.

Questions people ask

Why does my outside drain overflow when it rains?

Usually because the gully or the pipe below it is partly blocked, so it copes with normal use but not with a downpipe's worth of rainwater on top. Clearing and jetting the gully and its run usually solves it.

Can I put bleach or caustic soda in an outside drain?

It won't shift a real blockage and can harm the soakaway or the wildlife a surface water drain flows to. Mechanical clearing is safer and more effective.

My manhole cover is broken. Can you replace it?

Yes. Broken or rocking covers are a trip hazard and let debris in, and we can fit a replacement while we're clearing the drain.