Drainage Searches in London Property Conveyancing Explained
The drainage and water search is one of the standard searches carried out as part of the conveyancing process for every London property purchase. Understanding what the search reveals, what it does not cover, and how to interpret the results is important for any buyer, seller, or solicitor involved in a London property transaction.
What Is a CON29DW Drainage and Water Search?
The CON29DW is the standard drainage and water search document used in residential property conveyancing in England and Wales. The form provides answers to a set of standard questions about the drainage and water infrastructure serving a property, drawn from the records held by the relevant water and sewerage undertaker, which in London is Thames Water. Every residential property sale in London will include a CON29DW search carried out by the buyer solicitor, typically at a cost of between 50 and 100 pounds, with the cost included in the overall conveyancing quote.
The CON29DW search provides answers to questions including whether the property is connected to the public sewer, whether there is a public sewer within the boundary of the property, where the nearest public sewers are located relative to the property, whether the property is at risk of internal flooding from the public sewers, what the nature of the mains water supply to the property is, whether there is a water meter, and whether there are any outstanding notices or agreements relating to the drainage or water supply. The search is based on Thames Water records and is not a physical inspection.
Key Findings That Can Affect a London Property Purchase
The most significant potential finding in a CON29DW search for a London property is the existence of a public sewer within or close to the boundary of the property. Under the Water Industry Act 1991 and the associated sewer transfer legislation, a public sewer cannot be built over or constructed close to without the prior consent of Thames Water. If a CON29DW search reveals that a public sewer crosses beneath or near the property, any proposed extension, basement excavation, or significant landscaping work will require a build-over agreement or deviation consent from Thames Water before planning permission can be granted. This can have significant implications for buyers who are purchasing with a view to extending or developing the property.
The search will also reveal whether the property is listed on the Thames Water internal flooding risk register. Properties that have experienced internal flooding from the public sewer in the past are flagged on the register, and this information can affect insurance premiums and potentially the buyer decision to proceed with the purchase. A property shown as being at risk of internal sewer flooding may require flood mitigation measures such as an anti-flood valve on the drainage connection, which can cost between 500 and 1,500 pounds installed.
What the CON29DW Does Not Tell You
The CON29DW search is based entirely on records held by Thames Water and does not provide any information about the physical condition of the drainage system serving the property. A property can have a clean CON29DW search with no adverse findings and yet have an underground drainage system in a state of advanced deterioration. The search does not reveal whether the drains are cracked, collapsed, root-infested, or blocked. It does not confirm that the connections between the property drainage and the public sewer are intact and functioning. For this information, a physical CCTV drain survey is required.
The search also does not reveal whether there are any private drainage arrangements shared between the property and neighbouring properties. In London, particularly in older terraced housing, it is common for a drain to serve multiple properties before connecting to the public sewer. Responsibility for maintaining and repairing a shared private drain is governed by the common law principles of easement and shared benefit, and can be a source of dispute between neighbours if not addressed proactively.
Interpreting CON29DW Results When Buying a London Property
A buyer solicitor reviewing a CON29DW search result for a London property should draw the buyer attention to any sewer within or near the boundary, any internal flooding risk entries, and any outstanding notices or agreements. Where the search reveals a sewer beneath or near the property, the solicitor should advise the buyer on the implications for future development and on the process for obtaining build-over agreement consent from Thames Water.
For buyers who intend to carry out basement excavation, rear extension, or significant garden works, Prestige Engineers can carry out a pre-application assessment of the drainage position relative to proposed works, advise on Thames Water consent requirements, and manage the build-over agreement application process on behalf of the buyer or their contractor. We also provide the CCTV drain survey that complements the CON29DW search by providing a physical assessment of the drain condition.