Home / Topical Issues / Transfer of Private Sewers

Back to Topical Issues page

Transfer of Private Sewers


Using powers under the Water Industry Act, 1991 the government intends to transfer the responsibility for private sewers and some laterals to the water companies. This document aims to give an overview of the matters surrounding this transfer from the point of view of the drainage engineer. Further details regarding what is to be adopted can be found on the Department for the Environment, Food and Regional Affairs (DEFRA) web site.

Readers with long memories will recall that we have been here before. When the water industry was being prepared for privatisation in the mid to late 1980's there was talk of making all sewers into public sewers. In the event it was only section 24 sewers (of the Public Health Act, 1936) which were in fact made into 'full' public sewers. The change of heart may well have been so as not to scare away investors from the privatisation share issue but, there was a feeling held by many in the industry, that private sewers were a can of worms which was best left un-opened.

The government has been influenced by the public health and environmental problems associated with private sewers and there is a case for improving the way they are operated. For example, the author knows of a case where untreated sewage was flowing down the road in a residential area for days on end due to a blocked private sewer. The matter continued either because of absent property owners or because property owners were unwilling to accept their responsibilities.

Whilst the transfer of the responsibility for the private sewers to the water companies has much to recommend it, there could well be some unwanted consequences including increased costs and these will be discussed below.

Legal aspects of Transfer

First of all, however, it may be useful to define some basic terms. According to the Water Industry Act, 1991 a drain is “a drain used for the drainage of one building or of any buildings or yards appurtenant to buildings within the same curtilage”. The act makes the definition of the term sewer slightly more complicated but for the present purposes, a sewer is defined as “all sewers and drains (not being drains within the meaning given by this subsection) which are used for the drainage of buildings and yard appurtenant to buildings.” A private sewer is a sewer which is not a public sewer. The term lateral drain was introduced by the Water Act, 2003 by amending the Water Industry Act, 1991. The latter act now defines a lateral drain as “that part of a drain which runs from the curtilage of a building (or buildings or yards within the same curtilage) to the sewer with which the drain communicates...” or “the part of a drain identified in a declaration of vesting made under section 102...“ or under a section 104 agreement.

Section 105A of the Water Industry Act, 1991 was inserted by section 98 of the Water Act, 2003 and gives the Secretary of State power to regulate that the water companies adopt, under section 102 of the Water Industry Act,“sewers, lateral drains or sewage disposal works” within certain areas. Section 105A states that the water company will give notice to the owners of the private sewers in an area, that they intend to adopt the sewers under section 102. The owners then have two months to appeal. Draft regulations were published in August 2010 with the aim of the transfer taking place on 1 October 2011. A water company will have to publish notice of its intentions in the London Gazette and in local newspapers as appropriate.

Private pumping stations will not be transferred at the same time as the private sewers but this will be completed by 1 October 2016. There are other exceptions to the transfer including private sewage treatment works.

Background to Private Sewers

The author has to admit to being surprised, given the circumstances, by the lack of hard facts which exists regarding private sewers. According to DEFRA in their Impact Assessment on the policy (2008) there are approximately 323,000km of public sewers in England and Wales and the present measure is likely to add a further 184,000km of private sewers and some 36,000km of lateral drains. The total length of public sewer is going to be increased, therefore, by approximately 68%. Since there are no overall plans showing the location and extent of the private sewers these figures are obviously open to a good measure of doubt.

Almost all private sewers date from after 1937, the private sewers constructed before this date fell under section 24 of the Public Health Act, 1936 and were made into 'full' public sewers under the Water Act, 1989. The private sewers are mainly small diameter pipes probably laid with, at best, variable supervision in locations with difficult access for subsequent repair. Due to their location they are susceptible to connections, modifications and general abuse with little Building Control or other supervision. According to one estimate private sewers and drains suffer from 2.2 million blockages a year.

Reasons for the Transfer

The majority of householders probably do not know of their responsibility regarding the maintenance and repair of private sewers. This is likely to be because the vast majority of private sewers operate for years and years without a problem. It follows, therefore, that the transfer of private sewers will make no obvious difference to the majority of people. Those who stand to gain most are the owners of private sewers which are in a poor state of repair. An example of this might be a private sewer, located under the back gardens of a row of houses, which was poorly laid using pitch fibre pipes in the 1950's and which has been a periodic source of blockage and consequent flooding ever since. In such cases the public health department of the local authority would usually have become involved and would eventually replace the pipework and recharge the owners. A major problem the local authority faces is that the owners are jointly responsible for the repair of their private sewer and it can be exceptionally difficult to persuade all owners to contribute to repairs. The owners involved in such cases tend to be very vociferous and will probably have contacted their MP on numerous occasions. This might go some way to explain the implementation of the present measures.

It can be inferred that the overall condition of private sewers will be worse than that of the existing public sewers, however, there is little hard evidence to confirm this. A report produced in 2003 details CCTV sewer surveys of private sewers which were carried out at 30 locations in England and Wales but at sites where there were known problems as well as sites where there were no known problems. It was found that 17% of the private sewers were in poor condition (internal condition grades 4 and 5), excluding the exact lengths known to have structural problems. This cannot, however, be considered to be statistically representative of private sewers as a whole.

As already mentioned it currently often falls to local government to try to resolve problems in the private sewers and this can be time consuming, and so costly and this is probably a further reason for the government proceeding with the measure. There is also a link here with the measures being introduced by the Flood and Water Management Act, 2010 since central government aims to fund part of that Act's provisions with savings to local government by removing the need to deal with private sewer problems.

The problems with the present system for the management of private sewers, and the potential implications for public health and the environment can be illustrated by the problem mentioned in the introduction. The author noticed a few years ago that a manhole on a private sewer located under a vacant building plot was overflowing into the road and contacted the local authority. It still took many days before the matter was resolved and in the meantime the local children had to avoid playing in the sewage which was flowing over the pavement, across the road and into a road gully. The road gully connected into the surface water sewer which discharged into the local watercourse. In the above case, one would have hoped that the water company would have dealt with a simple blockage within a few hours. There is then likely to be a very significant public health and environmental benefit to the transfer of private sewers.

From the water companies point of view the transfer puts them in the position of being the manager of almost the whole system rather than, as is currently the case, only part. This will allow the companies to take a holistic approach and address problems throughout the system. For example, at present in cases of high infiltration flows in the public sewers a significant proportion of the infiltration probably comes via the private sewers if only because they represent a large fraction of the total length of the drainage system in the area. Infiltration is where water from the ground leaks into the sewer resulting in increased treatment costs at the sewage works and effectively reducing the capacity of the sewer downstream. In future water companies will have the opportunity to deal with most of the sources of the infiltration within an area, although under the proposals the majority of private drains will remain as a private responsibility. The transfer will mean that there will be one body, the water company, which is responsible for the majority of the drainage in a region rather than as at present, millions.

Private sewer contractors

One of the real losers from the transfer is likely to be the private companies which operate drain blockage clearing services, carry out repairs to drains and sewers and conduct CCTV sewer surveys. There have been some consultations and talk of the water companies employing the same drain clearing companies as currently do the work but some water companies have already tentatively set out their plans and they do not look encouraging from the existing contractors point of view. In any event it is difficult to envisage the water companies employing hundreds of different companies for clearing blockages in the long term. They will employ large firms under term contracts, as currently happens for maintenance, design work and construction for capital works, and so the small firms will be pushed out.


In 2008 DEFRA produced an Impact Assessment for the transfer of the private sewers and this was updated in 2010. They say in their 2010 report that the transfer will mean “...an average rise of £5 per bill from 2011 rising to £8 per year on all sewerage bills as all assets are upgraded by 2019-20, or from £3 to £14 per bill p.a. across different WaSCs. As above, the bill effects are highly uncertain, as quantities, and particularly the conditions and remedial costs for each water company area are unknown.” To put those figures into context, the 2008 report said that the average annual sewerage bill was about £160. The 2010 report says that initial capital spending of £957m would be required, mostly over the first 10 years. Averaging this over 10 years DEFRA arrive at a figure of £94m pa. The report says that the current operating costs of the private sewers is £193m and also estimates the annual operating costs of the adopted sewers as £166m averaged over the first ten years.

Between the 2008 and 2010 reports, the estimate of the initial one-off capital expenditure to bring the assets up to standard reduced from £1,291 to only £957m. This was despite the latest figures being based on the upgrading of 22,000, as opposed to 5,000 private pumping stations in the 2008 report. Meanwhile, very conveniently, the length of private sewer to be replaced fell from 16,500km in the 2008 report to only 5,500km in 2010. Given the lack of any hard reliable information and the wild changes in the figures used between estimates produced only two or three years apart, the costs are essentially meaningless.

In addition it is very difficult to have any confidence whatsoever in either report but particularly the 2010 version who's authors appear to have little knowledge of their subject matter. For instance the report is confused over the terms “pumping station” and “pump”. On page 13 the report talks about “...estimated cost of £1,500 (Ofwat estimated cost for WaScs to replace pumping stations)...”. The author presumes, based on the cost, they mean individual pumps within a pumping station. Elsewhere the report talks about (p10) “...either amalgamate pumps or decommission pumps, where alternative connections are available.” Again, this time based on the context, presumably they mean amalgamate or decommission pumping stations leading to the reduction in the number of pumps. This confusion is especially disappointing given the increased importance of private pumping stations due to the recent large increase in their estimated numbers.

To summarise the matter of costs, OFWAT said in November 2010 that there was “continued uncertainty surrounding costs of transfer”. Similarly the Consumer Council for Water's web site says, “...as the sewerage companies are unaware of the exact extent and condition of private sewers until transfer takes place, the exact cost of the transfer is unknown.” OFWAT also said that there was a “high likelihood” that the water companies would apply to increase water bills to pay for the additional costs associated with the transfer.

Incidental Costs

One additional cost of the transfer may concern property extensions since private sewers often run close to the properties they serve. If a householder wants to construct an extension over a public sewer it is possible for him or her to enter into a 'building over agreement' with the water company. This usually involves additional costs over and above that of building over a private sewer. In addition, in some circumstances the water company may require the householder to divert the sewer prior to constructing an extension and this can add very significantly to the overall cost.


It seems incredible to the author that government makes policy without knowing the scale of the problem and so cannot adequately estimate the cost implications. Presumably it takes this attitude because any additional costs will be paid for by the public through their water bills rather than through taxation for which the government is responsible. It seems that sewerage bills will shortly be rising by a significant but currently un-quantifiable amount at a time when many people have static or falling real incomes. It seems obvious to the author that following the transfer, the water companies will ask to put up water bills over and above the levels currently predicted due to the 'unforeseen problems' associated with private sewers. Unfortunately OFWAT will not be in a position to regulate the companies in an intelligent way due to a lack of any meaningful data.

Mention was made in the introduction of the problems of private sewers being a 'can of worms'. Given that the can of worms should be dealt with, then the present proposals are probably the best that can be expected. The author's feeling is that the measures are being implemented, however, without the full ramifications and cost implications having been fully appreciated.

Back to Topical Issues page

Copyright, 2011, Morton-Roberts Consulting Engineers Limited.
Last Modified 17 January 2011.