Flooding
Drains and sewers
Surface water is rainwater that drains from roads, roofs and paved areas. Waste or foul water is water from toilets, sinks, baths and other parts of a property.
If there is a blockage, responsibility usually depends on where the drain or sewer is, and whether the drain serves one property or more than one property.
Blockages are usually the responsibility of either Thames Water or the property owner.
Who is responsible for drains and sewers
The diagram below shows how drains and sewers connect to different types of homes. The sections after the diagram explain who is responsible for each type.
Drains serving one property
A drain is an underground pipe that serves one property. It is usually about four inches wide and carries surface water or foul water away from that property.
It usually connects to a public sewer.
The property owner is responsible for the drain up to the boundary of their property. Thames Water is responsible beyond the property boundary.
Sewers serving more than one property
A sewer is an underground pipe that serves more than one property. It may be on private land or public land.
Thames Water is responsible for all sewers.
Lateral drains
A lateral drain is a drain outside the boundary of the property it serves. It may be on public land or neighbouring private land.
Thames Water is responsible for lateral drains.
Road gullies and highway drains
Road gullies and highway drains collect surface water from roads. They do not collect foul water from properties.
We deal with blocked highway drains and road gullies if they cause surface water flooding.
Causes of blockages and defects
Private and public drains and sewers can become blocked or damaged.
Common causes include:
- fat building up in the pipe
- foreign objects, such as baby wipes, nappies or sanitary products
- poor design
- tree roots
- pipes with poor fall or the wrong size
- defective pipe sections or joints
If a blockage is in a drain serving one property, only that property is usually affected.
If a sewer is blocked, the first property affected is usually the one immediately upstream. Sewage may overflow there.
All properties upstream may eventually be affected because wastewater cannot flow away properly.
What to do if you think there is a blockage
Speak to your neighbours first to find out which properties are affected.
If only your property is affected, the blockage is likely to be in your private drain. The property owner or landlord is responsible for sorting this out.
You should arrange for a drainage specialist to clear the blockage. If you rent your home, contact your landlord or letting agent.
Tenants may be responsible, depending on their tenancy agreement and the cause of the blockage.
If more than one property is affected, contact Thames Water.
Contact Thames Water about drains and sewers.
If a blockage is not dealt with
Drain and sewer blockages can cause health risks if they are not dealt with.
If the people responsible do not take action, we may intervene. We may take formal action and arrange for the blockage to be cleared.
The people responsible will be charged for the work, including an administrative fee.