Drain Unblocking
Available 24/7. We clear blocked drains, sinks, toilets and gullies on the first visit in the vast majority of cases.
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Drain Mapping in Hertfordshire
What Drain Mapping Actually Is
Drain mapping is a scaled plan of the underground drainage on a site: the route of each run, the invert levels, the pipe sizes and where every connection goes. Architects, builders, developers and homeowners need that drawing for planning applications, extensions, new builds and water-company build-over agreements.
Doing it before you apply is cheaper than discovering a public sewer under the proposed kitchen, or a private run that has to be diverted after the foundations are in. We combine sonde locating with a CCTV drain survey so the plan is based on what is actually there, not on an old drawing that may be wrong or missing.
Why Architects and Builders Book Drain 247
A Drawing They Can Use
Not a verbal description of where we think the pipe runs. A scaled plan that drops into existing and proposed drawings.
Camera-Confirmed, Not Guessed
If we cannot see a connection, we say so. Water companies and building control prefer that to a line invented on site.
Invert Levels, Not a Sketch
Depths an architect or structural engineer can design to. Hertfordshire clay and pitch fibre need that accuracy.
Build-Over on the Same Visit
The CCTV survey a water company wants for a build-over agreement can be done while the camera is already in the run.
Older Drainage Systems
Victorian clay, pitch fibre and undocumented laterals are common around Watford. We map what is there, not what the deeds imply.
Fixed Price Before We Start
Quoted from what you tell us about the site. A typical house is a morning. Larger developments are priced separately.
Get a Drainage Plan Today
Drain mapping, drain tracing and a scaled drainage plan — booked now, so your extension, new build or build-over goes smoothly.
You get a drawing your architect can drop into existing and proposed plans: the route of each run, invert levels at the chambers, pipe sizes, and which connections look public or private. We confirm those lines with a camera, not a guess from an old deed plan.
Send the drawings through or call with the address and what the architect has asked for. We quote a fixed price before we start. Most houses around Watford are a morning's work.
What You Receive
The point of drain mapping is a pack your architect, builder or building control can act on — not a van ticket with an arrow on it.
A Scaled Plan
Runs plotted against the building, with chambers, gullies and connections marked.
Camera Confirmation
Footage of the runs we accessed, so the plan and the condition of the pipe sit together.
Invert Levels
Depths at chambers that an architect or structural engineer can design a fall to.
Public vs Private
Which runs look like yours and which look like a public sewer — the distinction a build-over application turns on.
Defects Flagged
If the map reveals a cracked or undersized run, we quote the repair rather than leaving you to find out later.
Usually a Single Visit
Most houses in Hertfordshire can be mapped in a morning. Larger sites are quoted separately.
Who Drain Mapping Is For
Architects
Existing and proposed drainage drawings, invert levels and pipe sizes you can drop into the planning pack without guessing a fall or a connection.
Builders
Know what you are digging towards before the excavator goes in. Depths, connections, and which runs you must not load or divert without consent.
Developers
Site-wide layout for new plots, connections and the drawings a water company or highway authority will ask for before they will talk about adoption.
Homeowners
Extensions, loft conversions, new bathrooms, or a solicitor who has asked for a drainage plan. Most houses around Watford are a morning's work.
How a Drain Mapping Visit Works
The camera, the sonde and the drawing are one job. We do not map a run we have not seen.
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Access and CCTV
We open the chambers we can reach and survey every run. That shows condition as well as route, which is what a build-over application also needs.
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Locate the Line
A sonde in the pipe and a locator above ground mark the route against the building, the garden and the proposed footprint.
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Invert Levels and Sizes
Depths at chambers, pipe diameters and the direction of flow, recorded so an engineer can design to them rather than assume a standard fall.
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The Drawing
A scaled plan with chambers, gullies, connections and notes on anything cracked, undocumented or likely to sit under the new work.
Drain Mapping for Planning and Build-Over Agreements
If you are building within three metres of a public sewer, or within one metre of a public lateral drain, your water company will usually require a build-over agreement before you start. Planning permission does not grant that consent. The application pack needs existing and proposed drainage drawings, invert levels, and often a CCTV survey of the run you intend to build over or near.
That is the job drain mapping is for. We produce the plan, confirm whether the run looks public or private, and can add the camera survey on the same visit. Thames Water covers most of the towns we work in; if you are with another sewerage undertaker the drawing still has to be accurate enough for them to accept it.
Skip it and the risk is not theoretical. A water company can refuse the agreement, building control can withhold a completion certificate, and a later buyer's solicitor can stall the sale. Mapping the site before the architect locks the layout is the cheap way to find out.
Drain Mapping, Drain Tracing and a CCTV Survey
People use these terms as if they were the same job. They are not, and mixing them up is why a lot of planning packs come back with a request for more information.
Drain mapping is the drawing: where the pipes go, how deep they are, what size they are and what they connect to. Drain tracing is the locating work that feeds that drawing — a sonde in the line so we can mark it on the surface. We do both on a mapping visit; tracing on its own is only useful if you already know you just need to find one run.
A CCTV drain survey shows the condition of the pipe — cracks, roots, scale, collapses — and where those defects sit along the run. Mapping without a camera is a guess at connections. A camera without a map does not tell your architect whether the sewer sits under the proposed kitchen.
Most extension and new-build jobs need both, which is why we quote them together when that is what the site requires. If you only need one lost run finding, say so and we will quote tracing on its own. If the camera shows a cracked or collapsed run, we quote the repair separately rather than mapping around a pipe that will fail.
Need Drain Mapping, Drain Tracing or a Drainage Plan?
Book it today so the project goes smoothly — or contact us and we will tell you what the visit needs to cover.
What Our Customers Say
Drain 247’s mapping saved our project from delays. Clear plans, fast service.
Great service and a great team of engineers. Wouldn’t hesitate to recommend to anyone. Work carried out to a high standard and the call-out was within the required time.
An absolute pleasure to deal with. George arrived at my house quickly to take care of a blockage in my drain. He cleared it in less than an hour and was very knowledgeable.
Related Drainage Services
CCTV Drain Survey
High-resolution inspections that identify structural problems, repeated blockages and hidden defects — with a report you can act on.
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Drain Repair
Patch lining, full relining and excavation repairs for cracked, collapsed or deteriorated pipework.
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Drain Jetting
High-pressure water jetting that scours fat, silt and scale from the pipe wall.
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Tanker Services
Vacuum tanker deployment for emptying, interceptors, and jobs too large for a van-mounted unit.
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Culvert Cleaning
Inspection and cleaning of culverts and larger surface-water runs for councils, estates and commercial sites.
Find out moreDrain Mapping Across Hertfordshire
Based in Watford. Drain mapping for homes, sites and developments across Hertfordshire and north west London.
- Watford
- St Albans
- Hemel Hempstead
- Rickmansworth
- Bushey
- Croxley Green
- Abbots Langley
- Kings Langley
- Chorleywood
- Berkhamsted
- Bricket Wood
- Cassiobury
- Moor Park
- Borehamwood
- Elstree
- Radlett
- Harpenden
- Potters Bar
- Hatfield
- Welwyn Garden City
- Harrow
- Pinner
- Northwood
- Ruislip
- Harefield
- Stanmore
- Edgware
- Hendon
- Barnet
- Brent Cross
- Wembley
- Enfield
- Aylesbury
- Milton Keynes
Common Questions About Drain Mapping
Do I Need Drain Mapping for an Extension?
If you are building near a public sewer you will usually need a build-over agreement, which starts with a survey and a plan. Even on a private run, knowing the invert levels stops the architect guessing a fall that will not work. If you are within three metres of a public sewer, or one metre of a public lateral, assume you need both mapping and CCTV until we have looked.
How Is Drain Mapping Different from a CCTV Survey?
A CCTV survey shows the condition of the pipe. Drain mapping shows where it goes, how deep it is and what connects to it. We often do both on the same visit because the camera is already in the run, and that is the pack planning and water companies actually want.
Is Drain Mapping the Same as Drain Tracing?
Tracing finds the pipe. Mapping puts it on a scaled drawing with invert levels, sizes and connections. People search both terms for the same job. If you need a plan for an architect or a build-over application, you need mapping, which includes the tracing.
Will I Get a Drawing I Can Give to My Architect?
Yes. The point of the visit is a plan they can drop into their drawings, not a verbal description of where we think the pipe runs.
What Is a Build-Over Agreement?
A contract with your sewerage undertaker — Thames Water in most of our area — allowing you to build over or near their pipe. Planning permission is not that consent. The application needs accurate drainage drawings; that is what our drain mapping visit produces. See our guide to build-over agreements if you want the legal side in more detail.
How Long Does Drain Mapping Take?
Most houses in Hertfordshire are a morning. A larger site, a block with shared drainage, or a new-build with several plots takes longer and is quoted separately. We tell you the likely window when we price it.
Can You Map a Property with No Manholes?
Often, yes, if we can reach the run from a gully, an inspection chamber, a rodding eye or an internal access. If we cannot get a camera and a sonde into the line we will say so, rather than inventing a route. Sometimes a small excavation to make an access is the honest next step, and we quote that before we do it.
Do You Map Commercial Sites and New Builds?
Yes. Developers, managing agents and commercial landlords book drain mapping for site layouts, disputed responsibility on shared runs, and the drawings needed before a connection or adoption conversation. Call with the address and what the architect or engineer has asked for.
How Much Does Drain Mapping Cost?
We quote a fixed price before we start, based on the size of the site and how many runs we need to access. A typical house is priced as a morning's work. We do not add a call-out fee. If the camera shows a repair is needed, that is quoted separately so you can decide.
Which Areas Do You Cover for Drain Mapping?
We are based in Watford and map drainage across Hertfordshire and north west London — including St Albans, Hemel Hempstead, Rickmansworth, Bushey, Harrow, Barnet and the surrounding towns. If you are slightly outside that, call anyway; mapping jobs are planned rather than emergency attendance.
Need a Drainage Plan for Planning?
We map the runs, invert levels and connections and hand you a drawing your architect or building control can use.