A CCTV drain survey before a Farnham extension

On a recent CCTV drain survey in Farnham, all nine pipe sections we inspected were flowing. There was no active blockage or backing-up during the inspection. The camera did, however, reveal fractures, displaced joints, broken sections and root ingress.

The property was due to be extended, so the planned drainage layout mattered. Some existing pipes would be replaced or rerouted. Others would stay in use after the building work, and their condition needed closer attention.

The drain that would stay in use

The property's wastewater collected in a private inspection chamber before leaving through a main drain. This outgoing pipe, often called the outfall, was expected to remain after the extension.

We found fractures near the start of the pipe, several areas where it had changed shape, and water pooling at one joint. That change in shape is known as deformation: the pipe is no longer fully round.

It was still carrying flow, but the combination of defects made it the main private drainage concern. Leaving it in service without addressing its condition could mean further deterioration or leakage after the building work.

Drain relining was a possible option to assess. This involves installing a resin liner inside the existing pipe to form a new structural lining. The final choice would depend on the pipe's condition and material, its measurements and the available access. Excavation or a combination of repairs could be more appropriate in some sections.

There were defects in several shorter branch pipes too, including displaced joints, a fracture and a broken section. Because these branches were expected to change with the extension, the sensible approach was to plan their repair, replacement or removal alongside the new layout. Any damaged pipe that remained in use would still need attention, and redundant branches would need to be properly disconnected, capped or removed.

The rainwater needed a better route

We also found a rainwater pipe ending at an open outlet close to the house. It contained deposits and root ingress, and no effective soakaway was identified.

Roof water discharged near a building can leave the surrounding ground saturated or cause ponding. Our recommendation was to replace this arrangement with sealed pipework leading to a suitably designed soakaway or another appropriate discharge point.

A soakaway lets collected rainwater disperse into the ground, but whether one will work depends on the site. Ground conditions, groundwater, available space and the size of the roof all matter. BRE365 percolation testing helps assess the ground before the design is settled. The CCTV survey itself did not establish whether a soakaway would be suitable here.

What we found further downstream

The downstream sewers raised a separate issue. Recorded in the survey as shared or public, they showed more serious defects, including numerous fractures, holes, broken sections, large joint displacements and extensive root ingress. Another shared run showed early joint displacement and root ingress before continuing off site.

Those findings needed to be passed to the relevant water authority to confirm responsibility and the next steps. Although the survey records indicated likely shared or public responsibility, they could not settle legal ownership. For a building project or property purchase, drainage searches, title information and asset records may also need to be checked with appropriate professional advice.

This is an important distinction when planning work: the condition of a pipe and who is responsible for it both affect what can happen next.

How the survey helped with the extension plans

The survey gave the project a clearer set of priorities. The main private drain needed a repair assessment because it would stay in use. The shorter branches needed to be considered as part of the revised layout. Rainwater disposal needed a suitable design, and the downstream sewer findings needed a response from the water authority.

These were recommendations from the inspection; this article does not describe completed repairs. A follow-up survey after repairs and construction could then help check the condition of the retained drainage.

For other homeowners planning an extension, the useful lesson is to understand the drains before working around them. A pipe can be flowing and still have defects that affect the plans. The findings here relate to the pipework we inspected, rather than establishing anything about neighbouring properties.

A CCTV drain survey records what the camera can see on the day. It cannot guarantee future performance or reveal problems in inaccessible or uninspected pipes, but it can give you useful evidence for the decisions ahead.

If you are planning an extension in Farnham and want to understand the drains first, get in touch for a quotation.