Sewer Map for My Property: How to Get One

Most people only go looking for a sewer map when it is already urgent. A build over agreement has been requested. A foundation trench has hit a pipe nobody expected. A buyer’s solicitor has asked a question that nobody in the chain can answer.

Here is the part that catches people out: the official sewer map almost never tells you the whole story about your own property.

Public records show the pipes the water company is responsible for. They do not show most of the drainage that actually sits under a typical garden or driveway. Understanding that gap is the difference between a smooth planning application and a very expensive surprise.

This article covers what a sewer map is, how to get one, what it will and will not show, and when you need someone on site with survey equipment instead of a PDF.

What is a sewer map?

A sewer map, sometimes called a sewer record or an asset location plan, is a drawing held by the statutory water and sewerage company for your area. It shows the public foul sewers, surface water sewers, combined sewers and rising mains that the company owns and maintains.

Each pipe is normally shown with an indication of its route, and manholes are usually marked with reference numbers. Depending on the record, you may also get pipe diameter, material and invert levels.

The key word is public. These are the assets the water company adopted. Anything private stays off the map in most cases.

Who holds the sewer records for my area?

Your water and sewerage company holds them. Which company that is depends entirely on geography rather than on who bills you for drinking water, because in some areas water supply and sewerage are handled by different companies.

If you are not sure who covers your postcode, the quickest route is to check with Water UK’s supplier lookup or simply search your postcode alongside “sewerage provider”. Once you know the company, their website will have a page for sewer records, asset location plans or property searches.

How to get a sewer map: four routes

There is no single national process, but in practice you have four options. Which one you choose depends on why you need the map.

1. Order an asset location plan from the water company

This is the direct route. You request a plan for a specific address or a drawn site boundary, and the water company sends back an extract of their sewer records covering that area.

You will usually need to supply the site address, a location plan or postcode, and payment. Turnaround varies by company and by how you order, so build a little slack into your programme if you are working to a planning deadline.

This is the option most designers, architects and contractors use at feasibility stage.

2. Free online sewer maps

Several water companies now offer a free online viewer where you can enter a postcode and see public sewer routes on a map. It is quick, and it is often enough to answer the basic question of whether a public sewer crosses the plot.

The limitation is that free viewers are usually simplified. You may not get levels, pipe sizes or the full detail you need to design around.

Use them for a first look. Do not use them as the basis for a foundation design.

3. A drainage and water search (CON29DW)

If you are buying a property, your conveyancer will normally order a drainage and water search as part of the standard searches. It includes a map extract showing public sewers in the vicinity, along with information about water mains, billing and whether the property is connected to the public sewer.

This is the route most homeowners encounter without ever asking for it. It is worth reading the plan rather than filing it, because a public sewer running through the back garden is exactly the sort of thing that constrains a future extension.

4. An on-site utility and drainage survey

The three routes above all give you plans. A survey gives you reality.

An on-site survey traces and locates drainage physically, lifting covers, recording manhole positions, taking invert and cover levels, and mapping pipe runs where they actually are rather than where a record says they should be. This is the option people reach for when the records are thin, contradictory, or simply do not match what is visible on the ground.

What a sewer map will not show you

This is where the trouble usually starts. Official records are genuinely useful, but they have well-known limits.

Private drainage is the biggest blind spot. The pipe from your kitchen to the boundary, the gully connections across a driveway, the run that serves a converted outbuilding: none of that is likely to appear on the water company’s map.

If your project depends on knowing exactly where those pipes are, records will not get you there.

Why people actually need a sewer map

In my experience the request nearly always comes from one of four situations.

• A build over or build near agreement. If you are building within three metres of a public sewer, the water company will want to know what you are proposing and how the asset stays accessible.
• Extension or new build design. Foundation type, drainage connections and even the footprint itself can change once you know where the sewer runs.
• Buying or selling. A public sewer under a garden affects what a buyer can do later, and it is far better discovered before exchange than after.
• Blockages and flooding. Working out whether a problem sits on your side of the boundary or the water company’s side starts with knowing which pipe is which.

The first three are design decisions. The fourth is a liability question. All four are cheaper to answer correctly at the start.

When you need a survey rather than a record

How do you know when to stop ordering plans and start booking a survey? These are the triggers I would look for.

The records and the site disagree

You lift a cover and there are three pipes where the plan shows one. Or the manhole on the drawing is not there at all. Once records and reality diverge, everything downstream of that plan becomes a guess.

You are designing foundations near a sewer

Approximate is not good enough when a pile position or a trench line depends on it. You need measured positions and levels, tied into a coordinate system your designer can work with.

The drainage is private and undocumented

Older properties, converted buildings, and sites that have been extended piecemeal over decades are the classic cases. The pipes exist. The paperwork does not.

You are combining drainage with other services

Drainage rarely sits alone. Electricity, gas, water and telecoms are usually in the same ground. A full utility survey using electromagnetic location and ground penetrating radar picks up the wider picture, so you are not solving one clash and creating another.

What an underground utility survey actually gives you

The output is not a sketch. It is a measured drawing you can design from.

A typical utility and drainage survey deliverable includes located service routes, manhole and chamber positions, cover and invert levels, pipe directions where they can be established, and the whole lot referenced to a survey grid and datum. It is normally issued as CAD, and it can be combined with a topographical survey so drainage and ground levels sit on the same drawing.

That combination matters more than people expect. Falls, gradients and connection points are all level-dependent, and a drainage plan without levels only answers half the question.

How the process works with us

1. You request a quote, and we send it back within 24 hours on business days.
2. We attend on the agreed dates and carry out the survey on site.
3. We process the data and produce the drawings.
4. You receive the deliverables a few days after the survey is complete, and we talk through any questions you have.

That last step is not a formality. A drainage drawing is only useful if the person designing from it understands what has been located, what has been inferred, and what could not be accessed on the day.

Practical tips before you order anything

• Know your boundary. A plan extract is only as useful as the site outline you supply with it.
• Ask for levels. If the water company can provide invert and cover levels, request them at the outset rather than going back a second time.
• Order early. Sewer information often sits on the critical path for planning and building control, and it is a poor thing to be waiting on.
• Keep the record. Store the plan with your property documents. The next owner, or the next project, will thank you.
• Treat every position as indicative until proven. Records inform design. Surveys confirm it.

Common questions

The bottom line

Getting a sewer map is the easy part. A postcode search, a search pack from your conveyancer, or an asset location plan request will all get you a drawing within a reasonable timeframe.

The harder question is whether that drawing answers what you are actually trying to decide.

If you need to know that a public sewer exists nearby, records will do. If you need to know exactly where a pipe runs, how deep it is, and what else is buried alongside it before you commit to a design or put a machine in the ground, then records are the starting point and a survey is the answer.

Get that distinction right at the beginning, and the sewer stops being the thing that derails your project.