Draining Map for My Property: How to Get One

A drainage map, also goes by the names; drainage plan, drainage layout, sewer map and asset location plan, depending on who is holding it.

There is almost certainly a plan of your drainage somewhere. Whether it bears any relation to what is buried in your garden is a different question entirely.

Local water authority plans are indicative at best. When we get to site, the covers shown on the plan are frequently in the wrong place, and sometimes they simply do not exist. The plans are generally out of date too, so later connections and relocated assets are missing entirely.

I have spent 22 years surveying underground services across England and Wales. Below is every route to getting hold of a plan, what each one costs, how long it takes, and how to tell whether the thing you are holding is good enough for what you are about to do with it.

What a drainage map actually shows

Three categories of pipe, and they are not treated the same:

• Public sewers. Owned and maintained by your water and sewerage company.
• Lateral drains. The length of your drain running beyond your boundary to the public sewer. Usually public owned.
• Private drains. Pipework inside your boundary serving only your property. Owned by you.

A water company map shows public sewers, lateral drains and the company’s own assets. In almost every case, your private pipework is not on it.

You will also see pipes classified as foul (waste from toilets, sinks and appliances), surface water or storm water (rainwater off roofs and hard standing), or combined (both foul and surface water in one pipe, common in older towns).

On 1 October 2011, most private sewers and lateral drains connecting to the public network in England and Wales transferred to the water companies. There were no comprehensive maps of them at the time, which is precisely why the transfer had to happen by public notification rather than by schedule. Private pumping stations followed on a staggered programme to 1 October 2016, and connections made after 1 July 2011 generally stay private unless adopted under a section 104 agreement.

Absence from a map proves nothing. Neither does presence.

How accurate does your drainage map need to be?

Everything hangs on what you plan to do with it.

An indicative plan is a reasonable starting point if you are:

• getting to know your own house
• chasing a recurring blockage, smell or wet patch
• working out whether a drain is shared and who pays for repairs
• dealing with an insurance question
• managing a rental
• answering a buyer’s question

An indicative plan is not evidence if you are:

• designing an extension, conservatory or garage
• relocating a manhole out of a new room
• designing foundations
• submitting a planning application that needs a drainage layout
• demonstrating Building Regulations Part H compliance
• applying for a build over agreement
• laying a driveway, patio or decking
• installing a soakaway, French drain or swale
• applying for an environmental permit
• breaking ground for any reason

Four lines worth remembering. Records tell you what somebody once drew. Site clues tell you what is visible today. A utility survey tells you where things actually are, to a coordinate and a depth. A CCTV survey tells you what is genuinely connected to what, and what condition it is in.

The most common confusion I see is clients assuming Ordnance Survey plans, title deeds and MasterMap are accurate enough to design on. On 95% of our surveys we find meaningful discrepancies between OS data and measured reality, typically 0.1 m to 5 m, and we have recorded 10 m on rural boundaries.

Once you are breaking ground this stops being a paperwork exercise. Hitting a high voltage cable or a gas main can be devastating.

When the plan shows a sewer that was never built

An engineering company was adding changing rooms and showers at a large school swimming pool and needed a drainage strategy. To get the wastewater away they had to tie into the main sewer running through the school, shown clearly on a local water authority plan. Nobody knew where it actually was.

The covers marked on the plan did not appear to be there. The routes did not go where the plan said. The caretakers, who had worked there for years, had never heard of the layout either.

We were brought in to do a utility survey and a CCTV survey i.e. to establish what drainage assets were on site, verify and locate the water authority assets and the main sewer, then map and record its condition, connectivity, line and level so the engineers could design the connection.

We surveyed the areas thoroughly with visual inspection, GPR and metal detectors, looking for buried assets. Nothing. So we started at the top of the indicated run and worked down. When we found a cover that looked about right, we put the crawler camera in and explored the routes. It turned out not to be the main sewer at all.

When we finally found a cover that was on the main sewer, that chamber was the start of the run, a considerable distance from where the plan said the run began.

Our conclusion: the mapped length of sewer was proposed and never installed.

The client caught it early with our help, but the new drainage strategy had to be completely rethought, because the plan was wrong. A record can show you a pipe that has never been in the ground because plans are made before the work takes place, and often the work deviates from the plan, and the plan is not updated.

Where to get an existing drainage map, and what each route is worth

So where do you actually get a plan from? There are six routes, and they are not equally useful.

1. Your water and sewerage company

Ask for a public sewer map or asset location plan, ordered online through the company’s portal or its mapping partner.

In England and Wales that means Thames Water (Property Searches), Severn Trent, United Utilities, Anglian Water, Yorkshire Water (SafeMove), Southern Water, Wessex Water (its Request a Map service is free), South West Water, Northumbrian Water, Dŵr Cymru Welsh Water and Hafren Dyfrdwy. DigDat is the shared mapping portal behind several of them.

Water pipes and sewer pipes usually sit on separate datasets, charged separately with a bundle discount, and the charge reflects the licensed Ordnance Survey base mapping underneath.

Limitation: public assets only, and the companies publish accuracy disclaimers for good reason. They should always be verified via a survey.

2. The free statutory route almost nobody mentions

Under section 199 of the Water Industry Act 1991, every sewerage undertaker in England and Wales must keep records of the location of each public sewer, lateral drain and disposal main vested in it. Sections 199(4) and (5) require those records to be open to free public inspection, in map form, at an office of the undertaker. Section 200 makes the council hold free copies for public inspection too.

Thames Water offers free viewing by appointment at a public access terminal at Clearwater Court in Reading. Wessex Water states it holds its sewer record maps under the section 199 duty and corrects historical errors when they come to light.

My view: the route is real but slow. Appointment, travel, view only, no data file. For most people, paying £15 to £30 for a download is a better use of a morning. The free route earns its keep in ownership disputes, or when you need to see whether a record has been amended.

Note what the Act does not ask for. Section 199(2) covers location, pipe type, effluent and ownership status. Not depth, not diameter, not material. And section 199(7) exempts anything laid before 1 September 1989 that the undertaker does not know about or cannot reasonably trace. That clause explains most of the blank space on your sewer map.

Limitation: free or paid, it is the same data, and it still will not give you a depth.

Source: Water Industry Act 1991, ss.199 and 200

3. Your council’s planning and building control records

Search the planning portal by address for drainage layouts submitted with past applications. The building control archive often holds as-approved drainage drawings, usually for an admin fee and a wait. A Freedom of Information request is a legitimate route where records are not published online.

Limitation: council records show what was approved, not what was built. Contractors move runs on site, and, as the school job proved, approved pipe runs sometimes never get installed at all.

4. Your own paperwork (and what Land Registry really shows)

Worth digging out: your conveyancing file; the drainage and water search (CON29DW) done at purchase, which reports on public assets and connections but not the route or condition of your private pipes; your solicitor’s scanned client file; previous building survey, homebuyer, mortgage or insurance reports; any previous CCTV drain survey; architect’s drawings; and drainage repair invoices, which often pinpoint a chamber.

Title deeds and Land Registry documents are worth a look, with expectations managed. The title plan shows general boundaries. The register may record drainage easements and rights, meaning who may drain through whose land. Neither is a drainage map. No pipe positions, no depths, no diameters.

Limitation: all historic paper, none of it checked against the ground since it was filed.

5. Ask the people who were there

The original developer or builder is your best bet on new builds, conversions and anything with pumped drainage. Then the previous owner, the neighbours (especially terraces and semis with shared laterals, where they may already hold a survey) and the estate agent who handled the sale.

On commercial, school and estate sites, talk to caretakers, site managers and maintenance staff. They are often the fastest way to find out a plan is wrong.

Limitation: memory is a cross-check, not a record.

6. What you can work out yourself in an hour

Scope this properly first. It is for understanding your own house and briefing whoever you hire. It is not a survey, and nothing you sketch here should be dug against or submitted anywhere.

• Lift accessible manhole covers and inspection chambers, and note flow directions and which pipe goes in what directions.
• Trace gullies, channel drains, soil vent pipes, rainwater downpipes, rodding eyes and air bricks back to chambers
• Count the chambers: several usually means separate foul and surface water branches
• Look for an interceptor trap, a sign of an older and often shared system
• Watch heavy rain: water sheeting off suggests a poor or absent soakaway

Two warnings. Chambers get buried under patios, driveways, decking, landscaping and extensions. And pipes very often do not run the route you would assume, so guessing before you excavate is a gamble.

One safety note. Covers seize. Do not force one, do not lean over an open chamber, and never enter one. Everything our surveyors record is done from ground level for a reason.

Sketch it, photograph it, keep it. It becomes the brief you hand a surveyor.

How a proper drainage map actually gets created

Covers lifted, dipped and levelled

On a standard topographical survey we lift all the drainage covers, whether or not that is stated on our quotation, so you know exactly what you are getting.

By the time we lift a cover, the total station has already recorded its size and level. Then we go at it with hand tools, because covers seize if they are not maintained, and we allow up to 15 minutes per cover. Anything we cannot lift is labelled as such on the drawing. Some are so badly seized they need breaking out by a groundworks team and reinstating.

Worth knowing: every cover on a drainage system should be liftable, because the day you have a problem is the day you need access.

Once a cover is off we record invert levels to the bottom of the chamber and to each pipe invert, pipe diameters, direction of flow and service type (foul or surface water), plus an acoustic connectivity check, sounding on a cover and listening for the echoes.

That is not even a full CCTV connectivity survey. Every observation is made from ground level, by visual inspection, with nobody entering the system. A good indication, but limited.

CCTV drainage surveys: when the indication isn’t enough

If drainage information is critical to your project, we would always recommend a CCTV drainage survey, because a camera lets you see what is actually going on.

A camera system is navigated through the pipework, confirming connectivity and revealing condition: hidden connections, shared runs, cracks, root ingress, displaced joints, deformation, scale, collapses and bad repairs. No plan will show you any of that.

We also run high-pressure water jetting in-house to gain camera access and clear light blockages and siltation. For heavier cleaning, larger obstructions or large diameter pipework we bring in a commercial HPWJ subcontractor with a JetVac tanker.

The deliverable is the useful part. CCTV data can be updated onto your topographical survey, so everything is coordinated in one drawing rather than a report in one folder and a plan in another.

A drain survey before you buy a house is not mandatory. It is still the thing I would recommend though to anyone before they buy because digging up your new home’s garden to fix a broken pipe you didn’t know about is not a risk worth taking.

Tracing, PAS 128 and why the topographical base matters

Finding the runs between chambers takes proper kit: a sonde and trace to pin down position and depth, multi-frequency digital locators (which pick up electricity, gas, water and telecoms in a single sweep), tracer dye to confirm what’s connected to what, acoustic location, ground penetrating radar for non-metallic pipe, and metal detectors for buried covers.

If you’re breaking ground, ask for PAS 128, the BSI specification for detecting underground utilities. It grades findings by quality level:

• QL-D — from records only
• QL-C — records checked against what’s visible on site
• QL-B — found by geophysical detection (graded B1 to B4)
• QL-A — physically confirmed by exposing the service, giving you exact position, depth, size, material and condition

Watch out for B4: this means a service the records led you to expect, but that wasn’t actually detected on site ( so it’s shown as an assumed route).

M-levels, meanwhile, describe how thoroughly the survey was done. M1 is roughly a 5 m grid, M2 roughly 2 m, and M4P the tightest spacing, with the most post-processing and the best chance of finding everything.

A topographical survey is required for PAS 128. Without one, a utility survey isn’t PAS 128 compliant. This is because the topo survey is what turns detected points into a coordinated, scaled drawing an architect can actually design on.

We work to plus or minus 15 mm, verified against independent control points. Compare that with a 1:1250 download stamped “indicative”.

Around half of our topographical surveys now include PAS 128 utility detection, and demand has climbed steadily as health and safety has become more ingrained in how people work.

The HSE’s HSG47 guidance sets out a plan-locate-excavate system: hand dig within roughly 0.5 m of a located service, and treat every cable as live until the owner confirms otherwise in writing. Industry estimates put UK utility strikes at over 60,000 a year.

One practical tip before you book anyone: ask for a sample report and site plan. Quality varies enormously — the same money buys you either a properly drafted CAD deliverable or a Word document with a hand sketch.

What a good drainage map must contain

• Horizontal position and depth of every run
• Cover levels, chamber depths and invert levels, to the chamber base and to each pipe invert
• Pipe gradient, diameter and material (vitrified clay, cast iron, uPVC, HDPE, pitch fibre)
• Service type (foul, surface water or combined) and flow direction
• Whether each run is shared or private
• Soakaways with depth and construction detail, plus septic tanks and treatment plants if you are off mains
• Discharge points, and any watercourses, springs or boreholes on or near the site
• On commercial and rural sites: storage areas for materials and waste, bunded areas with capacity, main water and sprinkler control valves, unmade ground, and emergency spill kits
• Any cover that could not be lifted, clearly labelled

Reading the symbols on a drainage plan

Read the legend before you read the plan. Circles for manholes and inspection chambers, arrows for flow direction, solid and dashed lines separating foul, surface water and combined, colour coding, and abbreviations such as IC, SW and FW.

Conventions vary between water companies and consultants.

Costs and timescales at a glance

What you get	Typical cost	Typical lead time
Water company sewer or asset map download (DigDat, SafeMove, Property Searches)	Around £15 to £30 per dataset, water and sewer priced separately with a bundle discount	1 to 5 working days
Viewing the public sewer map at a water company or council office	Free (statutory)	By appointment
Council building control archive copy	Admin fee	Days to weeks
CCTV drainage survey, single small domestic property (our pricing), including site survey, reporting and an indicative connectivity plan	£295 to £495	Half a day to a day on site, then 3 to 5 working days to report; next day possible if urgent and resources allow
Topographical survey with covers lifted, dipped and levelled	Quote-based	Quote-based
Topographical survey with PAS 128 utility detection	Quote-based	Quote-based

Budget CCTV quotes of £100 to £300 circulate online. But check what is included, because at that price, you are most often just buying a camera run and a video file, not a survey report with a connectivity plan you can hand an engineer.

And keep every report you commission. It saves paying twice at the next approval.

Build over agreements: the 3 metre and 1 metre rules

A build over agreement is a contract between you and your sewerage provider when you build over or near a sewer. It protects the network and preserves access for maintenance and repair.

Don’t be misled by the word ‘build over’. You still need one if you’re building nearby. Thames Water’s stated triggers are building within 3 metres of a public sewer, or within 1 metre of a public lateral drain. Other companies operate equivalent processes.

Planning permission does not grant permission to build over a sewer. They are separate consents from separate bodies, and you should not start before the agreement is in place, because the water company may require design changes.

For a new property, and for detached car ports and sheds, companies commonly require the sewer to be diverted rather than built over. Liability for damage during construction sits with the property owner.

Here is the part worth noticing. Thames Water itself advises that a builder or drainage specialist can survey to identify the location and size of sewers or drains within your boundary. The water company expects you to commission a survey where its own map is not good enough. We can help if you need a survey. Just give is a call.

What’s changing: NUAR, and the England/Wales split on SuDS

NUAR — the National Underground Asset Register — is a government-backed digital map showing where water, gas, electricity and telecoms lines are buried. Ordnance Survey was picked to run it in October 2024, a public test version went live in spring 2025, and the Data (Use and Access) Act 2025 made it official in law.

A few important limits: you can’t use it to look up your own house. Access is restricted to registered asset owners and their approved contractors. And it only covers utility networks, not the private drainage inside your property boundary. The same restrictions apply to LinesearchbeforeUdig (LSBUD).

On SuDS (Sustainable Drainage Systems) meaning the ways a site manages rainwater run-off. England and Wales have gone separate ways.

Wales brought in Schedule 3 of the Flood and Water Management Act 2010 back in January 2019. So most new developments there need sign-off from a SuDS Approving Body (SAB) and must include a surface water drainage layout.

England hasn’t done this yet. In January 2025 the government confirmed it would handle sustainable drainage through the normal planning system instead of switching Schedule 3 on. That position is still under review, and there have been signals that mandatory SuDS could come to England, so check the current requirement with your local planning authority before you design anything.

The bottom line: as the law stands today, a project in Wales faces a SAB submission that an equivalent English project does not.

The mistakes I see most often

Assuming plans exist, and that they are accurate and up to date. It is the biggest referencing mistake we see, and it rarely holds true. It ends the same way every time: an urgent, last-minute survey with the programme already under pressure. The school job is the extreme version, where the plan showed a sewer that had never been built.

Specifying the wrong survey because nobody asked what the job actually was. A client needed to locate a culvert but did not say so upfront, so a PAS 128 M2 was quoted when M4P was what the job needed. GPR across the full site with proper post-processing would have given a far better chance of finding it. Cheaper spec, worse outcome, same problem still buried.

Most clients do not fully know what they are asking for when they request a utility survey, and that is completely normal. Phone first on +44(0)143 884 1300 and describe the job rather than ordering a product you’re not 100% sure about.

Frequently asked questions

Does Land Registry show drains or drainage?

The title plan shows general boundaries only. The register may record drainage easements and rights, meaning who is permitted to drain through whose land, but neither shows pipe positions, depths or diameters.

How do I create a drainage map for my property?

Lift, dip and level every accessible chamber, trace the runs with sonde, EML and GPR, then confirm connectivity properly with a camera if it matters. Draw it all onto a topographical base so it is scaled, coordinated and usable by an architect or a water company.

Can I get a drainage map online?

Yes, from your water and sewerage company or its mapping partner, typically £15 to £30 and 1 to 5 working days (Wessex Water’s request service is free). It shows public assets only, and it is indicative.

Who owns the drain shared with my neighbour?

Since October 2011, most shared drains beyond your boundary are public and the water company’s responsibility. Pipework serving only your property, inside your boundary, is yours; if it is disputed, the section 199 record plus a trace will usually settle it.

My property isn’t on mains drainage. Is there a map?

No sewer map will help you. The tank or treatment plant, its pipework, the soakaway and the discharge point all need surveying and drawing, and environmental permit and consent-to-discharge questions depend on it.

Is a “draining map” the same as a drainage plan?

Yes. Drainage map, drainage plan, drainage layout, sewer map and asset location plan all describe broadly the same thing, and different sources use different names.

If the plan you have found is going to be dug for, designed on or submitted, get it verified on site. Ten minutes on the phone describing the job usually saves specifying the wrong survey. We cover England and Wales from four offices, work to RICS standards, and are accredited through ISO 9001, Constructionline Gold, CICES, TSA, CSCS and Acclaim.