Frequently asked questions

On this page you can read useful advice relating to the transfer of private sewers, drains and pumping stations.

A public sewer is a pipe that carries wastewater from more than one property, and has been laid or adopted by us.

Some groups of properties connected into a private sewer, which carries wastewater from more than one property, and may lie inside or outside of the boundaries of the properties they serve. 

The private sewer generally connects into a public sewer, where waste then gets taken away and treated.

These sewers are now owned and maintained by water and sewerage companies.

The lateral drain is the part of your private drain that lies outside of your property boundary under public land (the highway, footpaths, verges) or private land.

It connects either to a private sewer that drains to a public sewer, or directly to a public sewer.

Lateral drains are now owned and maintained by water and sewerage companies.

Private sewers come from a historical arrangement that dates from 1937.

Before that the 1875 Public Health Act made all sewers public.

This all changed with the 1936 Public Health Act, that meant all sewers from 1937 were only public if they were:

  • Already in place, or
  • Laid by a sewerage undertaker, or
  • Adopted by a sewerage undertaker

This is a historical arrangement was deemed complicated, inconsistent and unfair as those customers served by pre-1937 sewers received a more comprehensive drainage service for the same charge.

This is one of the reasons that the law was changed.


The decision by Defra to transfer responsibility to water and sewerage companies was made for the following reasons:

  • Most sewers are public (adopted) and are the responsibility of the water and sewerage company to maintain and repair. However, Government research suggested that there were about 125,000 miles of private sewers.
  • It is estimated that this affected up 10 million property owners, and many didn't realise they owned a private sewer until a problem occurred and they had to fix it at their own cost.
  • Some private sewers are in poor condition and suffer from blockages or collapses.
  • According to Water UK, collapses are relatively infrequent but can cost individual householders thousands of pounds to repair.
  • Private sewers can be either foul sewers (for wastewater) or surface water sewers (for disposing of rainfall from roofs and paved areas).


We are now responsible for the repair and maintenance of 107,000 km of sewers, an increase of 40,000km.  This includes clearing blockages, repairing and replacing pipes and ensuring that the sewer network runs smoothly.

As we have have only recently become responsible for the private sewers, we don’t know what condition they are in and therefore, what work they may need. For example, we previously cleared 55,000 sewer blockages a year and we expect this to increase to 250,000 a year.

This makes is very hard to calculate an exact cost of our new responsibilities.

The Government has estimated that the transfer could increase customers’ bills by between £3 and £14 per year. This small increase in your bill will protect you against the much larger one-off costs of clearing blockages and making repairs yourself.

We aim to minimise the cost of this transfer – and the impact on our customers’ bills.

We have written to the owners of all properties in our area that may be connected to our sewer network to notify them of the change in law regarding the ownership and responsibility for privately-owned sewers and lateral drains.

It was a legal requirement for us to inform you of the change.

Property owners are still responsible for some sections of pipe.  If you are concerned about your insurance policies, we advise that you speak with your insurer.

Any work carried out on shared drains and sewers before the transfer are the customer’s responsibilities.

We will not make any back payment for repairs before the transfer date of 1 October 2011 for private sewers.

This also applies to private pumping stations, meaning no back payments will be made prior to a station being confirmed eligible for adoption.

Read more about the transfer of private pumping stations

The Government also plans to introduce legislation to enforce the mandatory adoption of all new sewers and lateral drains. This legislation will be enacted through the Floods and Water Management Act 2010.

If you have any questions regarding legislation and design standards for developers, please contact our Developer Services helpdesk on 0800 009 3921 to discuss.

A pumping station pumps sewage under pressure from one point to another through a rising main.

A rising main is a type of drain or sewer through which foul sewage and/or surface water runoff is pumped from a pumping station to join with the main sewerage system.

Private Pumping Stations became eligible for adoption on 1st October 2016.

Before we can adopt a private pumping station, we first need to confirm it meets the eligibility criteria set out in The Water Industry (Schemes for Adoption of Private Sewers) Regulations 2011.

Once confirmed eligible we will confirm an adoption date with you.

No. Once we have adopted your pumping station we will be responsible for its maintenance and hence any costs associated with maintaining the pumping station will also become our responsibility.

Not yet. Rising mains are part of the second phase of the transfer and will be adopted with the eligible pumping station they are connected to.

If a rising main crosses public land and is serving a pumping station not eligible for transfer, the pumping station and rising main on private land will remain private but the section of rising main on third party land will be the responsibility of Thames Water on 1 October 2016.

Also in this section

How are you affected? Advice for property owners Private pumping stations