London sewer flooding prevention
We’re supporting our customers in London affected by sewer flooding in July 2021. The storms that caused this are rare, but we want to reduce the impact they could have on homes and businesses. To protect properties for the future, we're offering sewer flooding surveys for affected customers.
In total, we've contacted over 3,000 customers who may have been impacted by the July 2021 storms. We raised awareness of the survey offer by holding local events and using social media and community groups. We also collected responses from affected customers through an online questionnaire.
We've now surveyed almost 1,000 properties in the affected area. If you haven't already reported flooding at your property from 12 July 2021, please contact us:
- Email consultations@thameswater.co.uk
- Call 0800 316 9800 and quote reference 147944
Property surveys
Surveys allow us to assess which properties have a higher risk of sewer flooding. Along with the flood history from you and your neighbours, the survey tells us:
- How your property is connected to the sewer
- How many sewer connections it has and whether they are shared with other properties
- Which sewers it connects to and the size and depth of the sewer connections
- The type of property and how much of it drains to the sewer
If you don’t own the property, please contact the owner to arrange a survey.
High-risk properties
If the survey shows your property is at risk, we’ll install a sewer flooding resilience device. This will significantly reduce the chance of wastewater backing up into your property.
Low-risk properties
The survey may show that your property was affected by a different type of flooding. This could include surface water run-off from roads, a blockage or inadequate capacity of your private drains.
If the risk of further sewer flooding for your property is low, we won't install a device. We can give you a summary of the survey report, including layout of internal pipework and impermeable area calculations. This is in case you want to install your own flood mitigation measure. Please let us know if you do this.
For basements converted to habitable accommodation after 2002, we won't install a device. Property owners should undertake a flood risk assessment and carry out appropriate measures. We’ll check Building Regulations consents for alterations made to basement properties.
Sewer flooding resilience devices
Forge non-return valve
These are one-way valves used for properties that can’t be connected to a large trunk sewer. They’re often put in the lightwell of a property or outside the boundaries in the road.
WaStop non-return valve
These are one-way valves used when properties are connected to a large trunk sewer. The sewer must be safe to access and wide enough for an engineer to go into and install one.
Flooding local improvement process (FLIP)
These are one-way valves with added pumps to push flows from the property into a full sewer, when the valve is closed. We may install a FLIP if there's a risk to life or higher risk of flooding.
Selling your property
Having a sewer flooding resilience device alerts buyers to the risk of flooding. However, you’re legally obliged to inform purchasers of any issues, including flooding. With your agreement, we'll give your buyer advice and the opportunity to continue using the device.
Property insurance
We'll install a device if we find the risk of your property having sewer flooding is higher. Your insurer may or may not allow for this in the scope of your insurance cover. If they don’t, we recommend you shop around, starting with insurers who are part of the Flood Re scheme.
Preventing flooding risk for other properties
We'll use information from surveys and our computer models to ensure we don’t put anyone else at risk of flooding from this programme.
Liability
Please note, that the offer of the survey and any subsequent installation of flood protection does not imply that Thames Water is accepting liability for damage caused by any previous flooding at your property.