Blocked drain outside the house: how to clear it safely and when it is the water company's job

The short answer

Look at where the water collects, then clear leaves and silt from the grate with gloves. Do not use strong chemicals or lift heavy covers. If the blockage sits in a shared drain, it is usually the water company’s job.

Find where the water shows up

Outside drains come in a few types. A gully is the open grate near a downpipe or a wall. A manhole or inspection chamber has a lid over a deeper pipe. A gully that overflows after rain often has leaves or silt in the trap, since the trap holds water.

Walk round and note which drain is full. Check whether the water is clear rain or foul waste. Foul water has a smell, so keep away from it. Take photos, because they help a plumber and your water company.

Safe things you can try

Start with the simplest steps, because they carry the least risk.

1. Put on thick gloves and eye protection.
2. Lift the grate if it is light and loose, and remove leaves and silt by hand or with a small trowel.
3. Flush the trap with a hose, taking care not to push waste further in.
4. Run water from the kitchen and see if the gully drains.

If the water now drains away, watch it for a few days. A gully that clears but fills again still points to a problem further along.

What to leave alone

Some jobs are not safe for a home owner, although they look easy.

• Heavy covers. They can hurt your back or your hands, and you may fall into the chamber.
• Strong chemicals. They rarely clear a real blockage, yet they can harm old pipes and your skin.
• Rods in unseen pipes. You may push the blockage further or break a joint.

If sewage is in the chamber, keep children and pets away. Wash your hands well after any contact. Our guide to why drains block lists safe first steps inside the house.

What really causes outside blockages

Leaves and silt are common at gullies. Inside the chamber, the usual causes are fat, wipes and other waste, while roots are less common. Thames Water’s Bin it page says only pee, poo and toilet paper belong in the toilet. It also names fats, oils and grease, which build up and set.

Roots and displaced joints can also block a pipe. These need a camera to confirm. Our guide to CCTV drain surveys explains what a survey shows. Meanwhile, the cost guide sets out typical prices from two sources.

Whose drain is it?

Citizens Advice says a private drain inside your boundary is yours. A lateral drain outside your boundary belongs to the water company, as does a public sewer. A private sewer shared by several homes belongs to those owners. Many private sewers moved to the water companies in 2011, although some remain private.

So a blocked chamber at your boundary may not be your job. Ask the neighbours if they have the same problem, since a shared fault points to a shared drain. Read who is responsible for a blocked drain for more detail. Then see how to report a blocked drain or sewer for the next step.

Rented homes

If you rent, tell your landlord first, because they may have duties for the drains and the pipes. Our landlord plumbing checklist sets out the main points. Keep photos and dates of when the problem began.

Winter and flooding

Frozen pipes can stop a drain from flowing, so see frozen pipes in Northamptonshire. Clear water from a burst pipe is a different case. Turn off the water at the stop tap, and read where your stop tap is likely to be. Drainage trouble also varies by town, while blocked drains across the Nene Valley compares four.

Frequently asked questions

Is an outside blocked drain always my job?

No. A drain that serves only your home is usually yours. However, a shared drain or the pipe beyond your boundary normally belongs to the water company.

Can I pour boiling water down an outside drain?

Avoid it, because it can harm some pipes and fittings. It also rarely clears a deep blockage.

How do I stop it happening again?

Bin fat, wipes and nappies. Clear leaves from the gully each autumn, because they wash into the trap.

Get help with an outside drain

Our blocked drains service and CCTV drain survey service take requests through the online form. Mark it urgent if sewage is entering the home. Browse all our services or the areas we cover. Add your town and a short description, because that helps an engineer get back to you.

In Northampton, see blocked drain help in Northampton. Around Bedford, see plumbers in Bedford. In Kempston, see plumbers in Kempston. Near Lutterworth, see plumbers in Lutterworth. Each page explains local coverage, while the form works for every town.