Top of main content


Flooding from a sewer is one of the worst things that can happen to your home. If it’s affected you, or you’re worried it might, we’ve got guidance to help.

Watch our video to learn who to can help with different types of flooding.

If flooding is happening at your home, call us on 0800 316 9800. If it’s inside your property, it’s a good idea to contact your insurance company as they can help too.

Learn more about what to do when sewer flooding affects your home in our sewer flooding guide.

There are different organisations responsible for different parts of the drainage system. They all have their part to play in tackling the problem. Often the cause is hard to pinpoint, or outside anyone’s control – for instance, when a severe storm happens.

Flooding caused by heavy rain

All drains and sewers are built to handle normal showers every now and then. Sometimes when it pours down very heavily, the water doesn’t run away fast enough, and this causes flash flooding.  Many green areas in towns and cities have been concreted over. This means that instead of soaking into the ground, the rain fills the sewers. This sort of flooding often happens quickly and then stops suddenly. It’s also more likely to affect the outside of a property.

Learn more about what causes flooding in this video.

Combined sewers in London

Heavy rain can cause more problems in the capital because most of the sewer system is combined. This means that waste from toilets, bathrooms and kitchens flows into the same pipe as the rainwater that runs off roofs, drives and roads. Parts of the system can fill very quickly during intense storms.

Sometimes, this type of combined system won’t cope with the heaviest storms. It’s like filling a bath, although there’s an overflow, flooding will occur if the taps aren’t turned off.

Our response

When flash flooding has happened, we’ll collect information to understand how severe the situation is. This will also help inform decisions on upgrades to our sewer system.

Flooded roads

Drains in the road, known as gullies, and the pipes connecting them to our sewer are looked after by the local council.

Heavy rain can sometimes flood a road, but flooding is most often caused by a blockage in the gulley or connecting pipe. Rain running off your roof will usually connect into the same sewer. If that’s flowing away but water from the road isn’t, it often means there’s a blockage.

Please report problems with flooded roads to your local council.

River flooding

Rainwater from roofs and roads usually drain into rivers. If the river level is already high, then the water may have nowhere to go. It will then flood out of manholes, onto roads or gardens.

The flooding will usually look like dirty water without sewage. If you’re affected by river flooding, call the Environment Agency on 0800 80 70 60.

Groundwater flooding

This sort of flooding is where water gets into a building from the ground. This means it’s most likely to affect a basement. It will typically seep through walls or floors and build up over time, rather than appear suddenly. If you’re affected by groundwater flooding, call your local council.

Tell us about your experience

If your home or business was affected by flooding that has now cleared, please complete our survey. This will help us see where improvements may be needed.