A blocked drain is an inconvenience. A public sewer running beneath your garden is a legal constraint that could prevent you building an extension, a garage, or even a garden room, potentially for the life of your ownership. Drainage searches exist to surface exactly these kinds of issues before exchange, not after.
Yet they remain one of the least understood searches in the conveyancing process.
Lets dive in with our latest Five Minutes On theme.
What is a drainage search?
A drainage and water search, formally the CON29DW, is a regulated search product that provides information about a property’s connection to the public water and sewerage network. It is produced using data held by the relevant water and sewerage company for the area, and is a standard part of the residential conveyancing search bundle.
It answers 23 standard questions, covering:
- whether the property is connected to the public water supply and public sewer
- whether any public sewers or water mains are within the boundary of the property
- whether the property is at risk of internal sewer flooding
- the location of the nearest public sewer
- whether there are any current or planned drainage improvement schemes affecting the area
- the identity of the sewerage and water undertaker responsible for the area
Why does it matter, the sewer within the boundary issue
The single most consequential result a drainage search can return is confirmation that a public sewer runs within, or close to, the property boundary. This matters for one critical reason: building over or near a public sewer without consent from the water company is not permitted.
Under the Water Industry Act 1991 and subsequent legislation, water companies have a statutory right to access public sewers for inspection and maintenance. A building constructed over a public sewer without a formal build-over agreement creates significant risk:
- The water company may require the building to be demolished or modified
- Mortgage lenders may decline to lend against properties with unresolved build-over issues
- Future planning applications for extensions or outbuildings may be refused or conditioned
- Indemnity insurance may be required to proceed, and is not always straightforward to obtain
It is worth noting that since 2011, when the adoption of private sewers transferred many previously private drains into public ownership, the number of properties affected by this issue increased significantly overnight. Many homeowners, and even some conveyancers, remain unaware that the drain they thought was private is now a public asset.
Sewer flooding risk, an increasingly relevant question
The CON29DW includes a question on whether the property has been, or is at risk of being, subject to internal flooding from public sewers. With ageing Victorian infrastructure, increased rainfall intensity linked to climate change, and growing pressure on combined sewer systems, this is a question that is becoming more material, not less.
A positive response to this question, indicating a history of or risk of sewer flooding, should prompt further enquiry. It may also affect buildings insurance, and buyers should be made aware of the implications before exchange.
What a drainage search does not cover
Understanding the boundaries of the CON29DW is just as important as understanding what it reveals. It does not cover:
- Private drainage systems, septic tanks, cesspools, and private treatment plants are not covered. For rural properties or those not connected to mains drainage, a separate enquiry, and often a physical survey, is essential
- Surface water flooding, the risk of flooding from surface water runoff is covered in an environmental search, not the drainage search
- Drainage condition, the CON29DW confirms the existence and location of infrastructure, not its physical condition. A CCTV drain survey is required if condition is a concern
- Ordinary watercourses, ditches, streams, and ordinary watercourses fall outside the scope of the CON29DW and may require separate enquiry of the Lead Local Flood Authority
How to read a drainage search result
Drainage search results have historically varied in format and clarity between providers, sometimes making it harder than it should be to identify the most important findings quickly. The most critical questions to check are:
- Is the property connected to a public sewer? (If not, how is foul drainage managed?)
- Are any public sewers within the boundary of the property?
- Is there any history of, or risk of, internal sewer flooding?
- Are there any current water or sewerage improvement schemes affecting the property?
Where the answer to any of these is unexpected or concerning, further enquiry of the water company, or a formal build-over agreement where relevant, should follow before exchange.
A clearer report for a critical search
OneSearch has recently refreshed its drainage and water search report, the OneSearch DW, with a focus on clarity and usability. The revamped report is designed to surface the most important results prominently, making it easier for conveyancers to identify issues quickly and communicate them clearly to clients.
In a search that can have significant implications for development potential, mortgage lending, and long-term ownership, a report that is easy to read and act on isn’t a nice-to-have, it’s an essential part of good conveyancing practice.
A drainage search is one of the most consistently valuable searches in the residential conveyancing bundle; not because it always reveals a problem, but because when it does, the implications can be serious, expensive, and not always easy to resolve.
Understanding what it covers, what it doesn’t, and how to read the results is one of the simplest ways a conveyancer can add real value to a client at the point when it matters most… before they commit.
