CCTV drainage surveys
Drain Survey Before Relining
A relining specification depends on what the pipe actually looks like inside. A survey before relining records the defects, the bore, the connections and the condition of the host pipe, so the liner type, length and preparation can be chosen with evidence rather than assumption.
Why a survey comes before a lining specification
A cured-in-place liner is sized to the host pipe. If the pipe is not the diameter the drawings suggest, or if the bore has been reduced by scale, roots or a previous repair, a liner cut to the wrong size will not sit correctly. A survey before relining gives the information needed to specify the liner, the resin volume and the installation method.
The survey also shows what the pipe is made of. Clay, pitch fibre, concrete and plastic behave differently under cleaning and lining. Pitch fibre, for example, can deform and delaminate, and aggressive cleaning can make that worse. Recognising the material before work starts changes how the pipe is prepared.
We can help with CCTV drain surveys carried out before a relining specification is agreed, so the condition and geometry of the pipe are recorded first.
What the survey records
A survey for relining purposes is not just a general condition check. It needs to capture the details that affect whether a liner can be installed and how.
- Internal diameter at the start, end and at any change of pipe size.
- Material and joint type, including any mixed materials along the run.
- Location and orientation of connections, junctions and lateral entries.
- Deformation, ovality, dips and changes in gradient.
- Cracks, fractures, holes and missing sections of pipe wall.
- Root ingress, scale, silt and other deposits, with an estimate of how much bore is lost.
- Obstructions such as intruding seals, displaced joints or previous patch repairs.
Each observation is located by distance from the access point, so the liner length and any localised preparation can be planned against real positions rather than approximate ones.
Diameter changes and connections
Lining a pipe that changes diameter part way along is possible, but it needs to be known in advance. A liner is typically installed from one access to another, and if the pipe reduces or increases in size, the specification has to account for it. Any known or observed change in diameter should be recorded so the lining specification does not rely only on end measurements.
Connections matter for two reasons. First, a lateral entering the main run has to remain open after lining, so its position and size need to be recorded. Second, a connection can be a source of groundwater or soil entering the pipe, and that affects how the liner is expected to perform. A survey that notes connection positions by distance gives the installer a reference for reopening them.
Deformation, ovality and structural limits
Not every pipe can be lined without preparation. A pipe that has deformed, collapsed or lost a significant part of its cross section may need excavation, local repair or a different technique before a liner is considered. A survey shows the shape of the pipe, not just its nominal size.
Where deformation is present, the survey should record how much of the original bore remains and whether the pipe is still passable. This is a judgement about the pipe, not a guarantee that lining will work. The limits of any technique depend on the specific pipe, the product being used and the site conditions.
A camera survey shows visible internal surfaces. It cannot detect every defect, and it cannot see through deposits, standing water or a full pipe. Where the survey is limited, that limitation should be stated in the report.
Cleaning before the survey and before lining
Deposits hide the pipe wall. If a survey is carried out on a heavily silted or root-filled pipe, the report may describe the deposits rather than the pipe beneath them. Cleaning before the survey gives a clearer view, but the cleaning method has to suit the pipe material and condition.
High-pressure jetting at the wrong pressure can damage a fragile pipe, particularly pitch fibre or a pipe with existing fractures. Where cleaning is needed, it should be planned around what the pipe can withstand. In some cases a survey is carried out first to establish condition, then cleaning, then a second survey to confirm the pipe is ready for lining.
We can help with pre-lining surveys and with the follow-up inspection after cleaning, so the condition of the pipe is recorded at each stage.
Pre and post installation records
A record before lining and a record after lining serve different purposes. The pre-lining survey documents the condition that justified the work. The post-lining survey shows the finished internal surface, the position of reopened connections and whether the liner has wrinkles, folds or gaps at the ends.
Both records are useful for traceability. They do not, on their own, prove that the work complies with a specification or a standard. Whether a survey is graded, and to what system, depends on the agreed specification for that project. Not every survey is graded, and the coding used should be confirmed before the work is commissioned.
Where a project involves a public sewer or a connection to one, the water company’s requirements should be confirmed before a survey is specified. Different rules apply in England, Wales, Scotland and Northern Ireland, and the relevant authority may ask for specific information or a particular form of record.
Access and practical constraints
A survey is limited by what can be reached. Manholes, rodding points and inspection chambers provide entry, but some runs have no accessible point at one end, or the chamber is buried. Access arrangements affect how much of the run can be surveyed and how the liner would be installed.
Confined space work, including entry into a chamber or a large sewer, is safety-critical. It should be carried out by competent specialist teams working to a safe system, with the risks assessed before work starts. The HSE guidance on confined spaces sets out the duties that apply where entry cannot be avoided.
For building regulation matters in England, Approved Document H covers foul water drainage, pipe sizes and protection of pipes. It is a reference point for drainage work, not a substitute for project-specific design.
Related surveys and next steps
A pre-lining survey often overlaps with other work. If the pipe is being mapped, a drain mapping survey can record the layout at the same time. Where the concern is root growth, a root ingress survey focuses on the extent and position of roots. For a general condition record, a drainage survey covers the wider system.
If you are planning relining, the useful starting point is a clear record of the pipe as it is now. We can help with the survey work and with the reporting that supports a lining specification.
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Common questions
Frequently asked questions
Can a pipe be lined without a survey first?
It is possible to attempt lining without a survey, but the specification would be based on assumption rather than evidence. Diameter, material, connections and deformation all affect whether a liner will fit and perform. A survey before relining records those details so the specification can be matched to the pipe.
Does the survey need to be graded?
Not every survey is graded. Whether a grading system is used, and which one, depends on the agreed specification for the project. If a particular coding or grading is required, that should be confirmed before the survey is commissioned.
What if the pipe is too damaged to line?
A survey may show deformation, collapse or loss of section that makes lining unsuitable without preparation. In that case the options might include local repair, excavation or a different technique. The survey records the condition; the decision on method depends on the pipe and the project.
Is cleaning always needed before a pre-lining survey?
Not always. If deposits are light, the pipe wall may be visible enough to survey. Where silt, scale or roots obscure the pipe, cleaning before the survey gives a clearer view, but the cleaning method has to suit the pipe material and condition to avoid causing damage.
Do water company rules apply to relining?
Where a pipe is a public sewer or connects to one, the water company's requirements should be confirmed before a survey is specified. Rules differ between England, Wales, Scotland and Northern Ireland, and the relevant authority may ask for particular information or records.
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