Drainage survey technical review
An engineer's technical review of an existing drainage survey, interpreting the findings and recommending action.
About this service
A drainage CCTV survey produces a lot of information: a video, a long list of coded observations and often a contractor's recommendation to reline or dig up. What it rarely gives you is an independent view of how serious those defects really are. Our technical review interprets an existing survey from an engineer's point of view, explaining which defects matter, which can be monitored and what, if anything, needs doing.
This is useful when a buyer's survey flags drainage problems, when an insurer asks whether a leaking drain could be linked to cracking, or when a quote for repairs looks larger than expected. We read the footage alongside the report, check the defect coding against what we can see and relate the findings to the building. A displaced joint near a cracked bay window, for example, carries more weight than the same defect under a garden lawn.
If you do not yet have a survey, our CCTV drainage survey and report can be arranged first. If you already know the drains need fixing, our drain repair specification takes the next step. This review sits in between. It gives you an independent opinion on what the survey really shows, so you can make a sound decision before spending money on works, and it gives buyers, sellers and insurers a common basis for agreeing who does what.
When you need it
- You have a drainage survey and need an engineer's view
- An insurer or buyer needs drainage findings interpreted
What's included
- Review of survey footage and report
- Interpretation of defects and significance
- Recommendations
How it works
- Send us the surveyYou send the CCTV footage, written report and drainage plan, plus any related documents such as a structural report or insurer correspondence. We confirm the fee and scope in writing.
- Review footage and codingWe watch the relevant sections of footage and compare what we see with the coded defects, checking grading, location and whether anything has been missed or overstated.
- Relate defects to the propertyWe consider each defect's position relative to foundations, trees, boundaries and any visible cracking, and whether the pipe is a private drain, a lateral drain or a public sewer.
- Write recommendationsWe issue a short report grading each defect by significance, recommending action such as no action, monitoring, local repair or replacement, and noting who is likely to be responsible for each part.
What you receive
Not every drainage defect needs repairing
Drainage surveys use standard defect codes, and contractors sometimes treat every coded item as a repair. In practice, minor deposits, slight joint openings and light root fibres can often be cleaned or simply monitored, while fractures, displaced joints, collapsed sections and heavy root ingress near a building are more significant. The judgement turns on what the defect is doing to the pipe and to the ground around it.
Ownership is the other common question. Since 2011 most shared sewers and lateral drains serving more than one property, or running outside your boundary, have been the responsibility of the sewerage company, which in most of London is Thames Water. Defects in that section may be theirs to repair. Our review flags where responsibility probably lies, so you do not pay for work that is not yours.
Frequently asked questions
How do I read a drainage CCTV survey report?
Most reports list each pipe run with observations recorded at distances along the pipe, using standard codes for defects such as cracks, fractures, displaced joints, roots and deposits. Many also give an overall grade. The difficulty is judging how much each item matters in practice. An engineer's review relates the findings to your building and explains which defects are serious and which are minor.
Can a damaged drain cause subsidence?
It can. Water leaking from a broken drain can wash fine material out of sandy or gravelly ground, or soften clay beneath shallow foundations, leading to settlement. In London Clay, tree roots are a more common cause of movement, but leaking drains can still contribute. Our subsidence guide explains how engineers work out which cause is responsible.
Is relining always necessary if a drain survey shows defects?
No. Relining is a good repair for cracked or leaking pipes that are still broadly in shape, but it is not needed for every defect. Light deposits can be jetted, minor root ingress can be cut and monitored, and a single bad joint may only need a local patch. Badly displaced or collapsed sections may need excavation instead. An independent review helps you choose the right option.
Who is responsible for drain repairs in London?
Generally, you are responsible for the drain serving only your property and lying within your boundary. Once a pipe serves more than one property, or runs beyond your boundary to the sewer, it is usually the sewerage company's responsibility, which in most of London means Thames Water. There are exceptions, so the drainage layout needs checking against the survey before you commit to repairs.