Homebuyer Drain Survey and Drain Condition Report

A homebuyer drain survey, also called a pre-purchase CCTV drain survey, puts a camera through the below-ground drainage serving the property and produces a drain condition report: what the pipes are made of, where they run, what defects exist and where, and what it would cost to put right. Victorian clay drains with displaced joints, root ingress and collapsed sections are common across London and Surrey, and drainage defects are also a frequent hidden cause of damp at the base of walls.

What the survey records

• Each run surveyed, its material (vitrified clay, PVC, pitch fibre, cast iron) and diameter
• Defects recorded by chainage, the distance from the point of entry, so a contractor can find them: displaced and open joints, fractures and cracks, deformation, root ingress, encrustation and scale, settled deposits and silt, standing water indicating a back-fall, and collapses
• Evidence of earlier repairs, linings and patches
• Gullies, inspection chambers and rainwater connections
• Drain mapping with a sonde locator where the layout is unknown, showing the line and depth of the drain under driveways, extensions and gardens
• Whether the drain is private or shared, and where responsibility transfers to the water company
• Still images at each observation and a plain-English assessment of significance

Questions a drain survey answers for a buyer

• Has an extension or conservatory been built over a drain, and is there a build-over agreement with Thames Water or the relevant sewerage undertaker?
• Is the damp at the front wall coming from a cracked gully or a broken rainwater connection?
• Are there cross connections between foul and surface water, confirmed by dye testing, that a water company could require you to correct?
• Do roots from that tree need dealing with now or in five years?
• Is the smell in the garden a defective interceptor trap?
• Will the proposed basement or extension conflict with a sewer?

Drains and damp

A leaking drain against a wall keeps the ground permanently wet and can produce staining indistinguishable from rising damp. When we investigate damp at low level near a gully, chamber or soil stack, a drain camera is part of the evidence, and the drain survey can be combined with a pre-purchase damp survey in one visit. Equally, a sound drain is a useful negative result: it allows the drainage to be excluded so the real cause can be addressed.

Insurance and repairs

Many buildings policies cover accidental damage to underground services, and a survey that dates and describes a defect supports a claim. Where repair is needed, the options are usually no-dig patch lining, full lining or excavation, and the report describes which fits each defect. Drainage works are quoted separately by our team or any drainage contractor against the report. DML does not carry out the repairs, so the survey is not a sales exercise.

We investigate across Greater London and Surrey. See areas we cover.

Frequently Asked Questions

Related services

• CCTV drainage surveys
• Drainage inspections
• Pre-purchase damp survey
• Soil pipe and waste leaks
• For estate agents

Related reading: Why a CCTV drain survey matters before you buy a house · When you need a CCTV drain survey