How much does drain mapping cost?

Drain mapping for a typical residential property costs £250 to £500, depending on the size of the system and number of access points. Larger properties or commercial sites with more complex drainage may cost £500 to £1,000 or more. We include the CCTV survey, sonde tracing, and a full report with scaled plans. We'll give you a fixed price before we start.

What's the difference between drain mapping and a CCTV survey?

A standard CCTV survey inspects the condition of your pipes - looking for cracks, blockages, and damage. Drain mapping goes further. We use sonde tracing technology to pinpoint the exact location and depth of every pipe from above ground. The result is a scaled plan showing your entire drainage system, not just footage of what's inside the pipes.

What's included in a drain mapping report?

Our reports include a scaled plan showing all drain runs, pipe locations and depths, pipe materials and diameters, manhole and inspection chamber positions, flow directions, connections to the public sewer, condition assessment of all visible pipework, and recommendations for any repairs needed. Reports come in PDF format, with CAD files available on request.

Do I need drain mapping for a build over agreement?

Usually, yes. Water authorities need to know exactly where their pipes are before they'll approve building work near or over them. Our drain mapping reports include all the information they require - pipe location, depth, condition, and your proposed building's position relative to the drainage. We can also carry out the post-build survey once your work is complete.

How long does drain mapping take?

Most residential properties take 1 to 2 hours to survey. Larger properties or those with complex drainage systems may take half a day. Your report is typically ready within 24 to 48 hours. If you need it urgently for a build over application or property purchase, let us know and we'll prioritise it.

Can drain mapping find drains that aren't on any plans?

Yes - that's often why people need it. Many properties have drainage that was never properly recorded, or that's been modified over the years without updating the plans. Our sonde tracing equipment locates pipes from above ground, even when there are no visible access points. We regularly find drains that owners didn't know existed.

What equipment do you use for drain mapping?

We use HD CCTV cameras to inspect inside the pipes, combined with sonde transmitters that emit a signal we can trace from above ground using a receiver. This lets us map the exact route of each drain and measure its depth at multiple points. For larger sites, we can also provide GPS coordinates for integration with site plans.

Is drain mapping required when buying a house?

It's not legally required, but it's highly recommended - especially for older properties. Standard homebuyer surveys don't cover drainage, and problems can be expensive to fix. A drain mapping survey before you buy reveals any hidden issues and shows you exactly what you're taking on. Some buyers have saved thousands by using our reports to renegotiate the sale price.

What's a build over agreement?

A build over agreement is permission from your water authority to build over or near a public sewer. Since 2011, building regulations require this for any construction within 3 metres of a public sewer. The water authority needs to be sure your building won't damage the pipe or block their access for maintenance. A drain mapping survey provides the evidence they need.

Can I see shared drains with my neighbours?

Yes. Our surveys identify where your drainage connects to shared systems and public sewers. This is important because responsibility for repairs changes depending on ownership. Private drains within your property boundary are your responsibility, but shared drains and lateral drains became the water company's responsibility in 2011.

How accurate is drain mapping?

Very accurate. Sonde tracing typically locates pipes to within 100mm horizontally and provides depth measurements accurate to around 50mm. This is far more reliable than old paper plans, which often show drains in the wrong place or miss sections entirely. For critical building projects, this accuracy can prevent costly mistakes.

Drain mapping

Know exactly what's under your property - before you build, buy, or dig.

Detailed plans showing pipe locations, depths, and routes

Reports accepted by water authorities for build over agreements

Identify shared drains and public sewer connections

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Why choose OneFlow?

based on 180+ Google reviews

No callout fees

You only pay for the survey itself. No hidden charges for travel, equipment, or access - the price we quote is the price you pay.

Same-day reports

Most residential drain mapping reports are ready within 24 to 48 hours. Need it faster? We can prioritise urgent requests for build over applications.

Solicitor and architect ready

Our reports include everything solicitors, architects, and water authorities need - scaled plans, pipe depths, materials, condition assessments, and recommendations.

CCTV and tracing included

Every drain mapping survey uses HD CCTV cameras and sonde tracing equipment. You get accurate locations and depths, not guesswork from old plans.

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Surveys completed in under 2 hours

Full mapping for most residential properties - with your report delivered within 48 hours.

98%

Of customers would recommend us.

3000+

Jobs completed last year alone.

Why you need to know what's under your property

Old drainage plans are often wrong - or don't exist at all. Pipes get moved, extended, and connected without records being updated.

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Planning an extension or building work

If you're building within 3 metres of a public sewer, you'll need a build over agreement from your water authority. They'll want proof of where the drains are.

Buying a property

Standard homebuyer surveys don't cover drainage. A drain mapping survey shows you the full picture - hidden defects, shared drains with neighbours, and potential problems.

Why choose a local team?

See how we compare to the big brands.

The big names

What you often get with the big names.

Basic video with no measurements or mapping

Reports that water authorities reject

Days or weeks waiting for your report

Call centres that can't answer technical questions

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OneFlow

What you get when you call us.

Full CAD-ready plans with depths, materials, and condition

Reports accepted by all local water authorities

Most reports delivered within 48 hours

Speak directly to the engineer who did your survey

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Drainer of the
year 2025

The Drainage Awards

What our customers say

Real reviews from real customers.

“Called at 6am with sewage coming up through the shower. Engineer arrived before 8, fixed it within the hour. Can't thank them enough.”

— James T, Southampton

“Third company I'd tried that week. The other two never showed. OneFlow answered, turned up same day, and actually fixed it. Should have called them first.”

— Michelle R, Brighton

“No messing about. Showed me the camera footage, explained what was wrong, gave me a price, and got on with it. Exactly how it should be.”

— David H, Portsmouth

“Blocked drain on Christmas Eve. Thought we'd be stuck for days. They came out that evening and sorted it. Absolute lifesavers.”
‍

— Sarah K, Guildford

“We've used them for three rental properties now. Always answer the phone, always turn up, always fair on price. Hard to find.”
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— Mark L, Bournemouth

“Engineer was honest and said we didn't need half the work another company had quoted for. Saved us hundreds. We'll use them every time now.”

— Karen W, Winchester

“Toilet blocked on the morning of our daughter's birthday party. They had someone here within the hour and sorted it before the guests arrived.”

— Rachel M, Crawley

“Other companies quoted over the phone then doubled it on arrival. OneFlow quoted £180, charged £180.”
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— Tom S, Bournemouth

“Drainage issue had been misdiagnosed twice by other firms. OneFlow found the real problem in ten minutes with their camera. Fixed the same day.”

— Angela D, Eastbourne

“Rang at 11pm expecting to leave a voicemail. Actual person answered. Engineer here by midnight. Didn't think companies like this still existed.”

— Chris B, Woking

FAQs

Still have questions?

Get in touch with our friendly support team.

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Need your drains mapped?

Same-day availability. Reports within 48 hours.

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90-minute average response across the UK.

★★★★★ based on 180+ Google reviews