Gully or main drain?
Outside, there are two common places for a blockage. The first is a gully: the small grid at ground level where a kitchen waste pipe, a downpipe or a washing machine discharges. These catch leaves, silt and, very often, grease from the kitchen sink. Water pooling around the grid while everything inside drains normally usually points to a gully.
The second is the main underground drain. If the inspection chamber (the larger rectangular or round cover) is full of water, or several fittings indoors are slow at once, the blockage is further down the system.
Safe first steps
Before doing anything else, stop using water inside: no baths, washing machines or dishwashers until the drain is running. Every litre has to go somewhere, and if the drain is blocked it will come back up.
Clear the gully grid
Wearing rubber gloves, lift off the grid and scoop out leaves and debris you can reach. Rinse the grid and replace it.
Skip the chemicals
Do not pour bleach, drain unblocker or boiling water into an outside drain. It rarely helps and makes the job less safe for whoever clears it.
Never go in
Do not climb into or lean right over a chamber. Keep children and pets away from any open cover.
Finding the chamber that is full
If you have more than one inspection chamber, they are connected in a line running away from the house. Lift each one carefully and look inside. A blockage sits between the last full chamber and the first empty one. If the chamber nearest the house is full and the next one is empty, the blockage is in the pipe between them. Knowing this helps whoever clears it, and it also tells you something about who is responsible.
Covers can be heavy. Use a proper lifting key or a flat tool, bend your knees and slide rather than lift where you can. Put the cover back firmly afterwards.
When it is probably the water company's
If your own chambers are empty but water is not getting away, or the full chamber is one your neighbours also drain into, the blockage is likely in a shared pipe. Shared drains are usually the water company's responsibility, and they may clear it free of charge. Our guide on who is responsible for drains explains how to tell.
Your water company's website will have a page for reporting a blocked sewer, and many let you do it online or by phone at any time.
When to call for help
Some situations need attention straight away rather than more DIY.
Water backing up
Water rising in toilets, showers or ground-floor sinks.
Sewage in the garden
Waste overflowing from a chamber or gully onto the ground.
Several slow fittings
More than one fitting in the house struggling at the same time.
A blockage that returns
The same gully or chamber filling again soon after clearing.
After it is cleared
A one-off blockage often has a simple cause, such as a build-up of leaves or a lump of fat. If it keeps happening, ask for the drain to be checked with a camera. Roots, a cracked pipe or a sunken length are common hidden causes, and dealing with them saves repeated call-outs. Our guide to drain unblocking costs explains when that becomes the better option.
Keeping gullies clear helps too. Fit a grid that sits flush, scrape fat from pans into the bin before washing up, and sweep leaves away from outside drains in autumn.
Get it cleared
See how we clear blockages on our drain unblocking page, or send us a message with your postcode and what you can see in the chamber.
Frequently asked questions
Why does my outside gully keep filling with water?
Usually grease from the kitchen sink or a build-up of leaves and silt. If clearing the grid does not help, the pipe beyond it may be blocked.
Can I use a hosepipe to clear an outside drain?
A hose can help rinse a gully, but it will not clear a solid blockage in the main drain and may cause it to overflow.
Is it safe to lift a manhole cover myself?
Small domestic covers can be lifted carefully with the right tool. Never enter the chamber, and keep others away while it is open.
What if the full chamber is on my neighbour's side?
That suggests a shared pipe. Talk to your neighbour and contact your water company, which is usually responsible.