Underground drains are important but largely hidden. Defects can cause blockage, leakage, odour, damp ground and, in some soil conditions, loss of support near foundations. A home survey can observe accessible components and warning signs, but it is not a comprehensive drainage test and cannot confirm the condition of every buried pipe.
The inspection level and safe access matter. In a detailed RICS Level 3 inspection, accessible chamber covers may be lifted where this can be done safely and without damage, and normal operation may be observed. Covers beneath heavy objects, sealed covers and drainage outside the property boundary may remain unavailable.
Visible components
The surveyor considers gullies, soil and vent pipes, waste connections, chamber condition and the apparent route of drainage. Signs such as standing foul water, deposits, displaced channels, cracked covers, root entry or slow discharge can justify further investigation. Surface-water arrangements are also considered where visible.
What is not tested
A home survey does not send a camera through the pipework, perform pressure or dye tests, map every connection or confirm legal ownership. Water may not be run through every appliance. Some defects are intermittent or lie beyond the accessible chamber, so apparently normal flow at one moment cannot guarantee a sound system.
Clues elsewhere
Repeated blockage history, local ground settlement, unexplained low-level damp, odour and cracking near a drain route may add concern. Each has other possible causes. The surveyor should bring the evidence together rather than using one symptom to declare a drain broken.
When CCTV is useful
A CCTV survey can be proportionate where there are visible defects, a history of blockage, suspected leakage, significant mature vegetation or movement potentially associated with drains. The brief should identify the relevant runs and ask for pipe material, alignment, defects, connections and repair recommendations. Images and a plan are more useful than a simple pass-or-fail statement.
Documents and responsibilities
Your conveyancer should establish public or shared sewer arrangements, easements, adoption and responsibility where relevant. Ask for invoices and reports from earlier repairs. Building over or altering drains may require approvals. Physical condition advice from the surveyor complements, but does not replace, these legal enquiries.
If a report recommends repair, obtain a plan showing affected sections, access needs and whether excavation crosses a boundary or shared surface. Pipe lining, local repair and replacement each have limitations and should follow defect type and pipe condition. Confirm how the repaired run will be tested and what evidence will be provided on completion. For shared systems, coordinate the scope so that a local repair does not overlook an upstream blockage or a defective downstream connection.
- Keep CCTV footage and a labelled drainage plan
- Confirm who owns shared sections
- Check connections serving extensions
- Ask how completed repair will be verified
Advice for your property
Get the right professional inspection
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Authoritative sources and further reading
The guide is general information, not property-specific, structural, legal, tax or financial advice. Source pages can change; consult the relevant professional for your circumstances.