Soakaway surveys: what a camera can and cannot tell you

Defra's sustainable drainage guidance describes a soakaway as an underground structure receiving surface water for infiltration. This page concerns rainwater, such as drainage from roofs or paved areas. It is not advice on the drainage field of a septic tank or sewage treatment plant.

Find any drainage plan, installation record or maintenance instruction you already have. Note which downpipes or surface drains are thought to connect, but distinguish a documented connection from an assumption. If you cannot establish whether the system carries rainwater or sewage, tell the investigator that before booking. Do not open covers or add substances to find out.

Sources: Defra; HSE.

A camera inspection can only report on what the operator can reach and see. DASA notes that obstructions or standing water can limit footage. Ask where the proposed camera run starts and ends, and whether the quotation actually includes assessment of the receiving soakaway.

Defra's England guidance treats suitable ground conditions and infiltration assessment as design questions. Our practical conclusion is that a clear pipe video should not be presented as a measured ground-infiltration result. Ask the drainage specialist or designer which additional assessment, if any, is needed for your problem; do not assume a generic CCTV package includes it.

• Pipe condition: which accessible length was inspected?
• Destination: was the connection to the soakaway established?
• Performance: what evidence supports the assessment of the receiving system?
• Ground: was infiltration assessed, or is that outside this visit?

Sources: DASA; Defra.

Before the appointment, write down where water appears, whether it follows rainfall, roughly how long it remains and whether the same thing happened before. Add photographs taken from a safe, dry position and note any recent roof, patio or driveway work. This is an observation log for the investigator, not a way to diagnose the cause yourself.

Avoid turning 'water remained beside the downpipe after rain' into 'the soakaway has collapsed'. Keep the observation separate from any explanation someone has suggested. If the problem is intermittent, ask whether the investigator needs particular conditions or further monitoring to answer the question. Never enter floodwater or a chamber to obtain a better photograph.

Sources: Defra; HSE.

England's Approved Document H explains that infiltration drainage is not suitable in every situation. Do not choose a replacement simply by matching the size of an old chamber or by accepting a camera-only conclusion about the soil. Ask who is responsible for the proposed design and what site information supports it.

Request a written distinction between the observed problem, any uncertainty and the proposed remedy. Ask how the proposal accounts for the area draining into the system and the destination of water. The designer should identify the applicable requirements and any permissions. England's cited documents are not a UK-wide approval or a homeowner installation recipe.

Sources: Approved Document H; Defra.

Ask each business to itemise the initial visit, pipe inspection, tracing, any specialist assessment and the written findings. Check whether excavation, reinstatement or a return visit is excluded. Request an explanation before authorising extra work, including what useful evidence it is expected to produce.

Agree a stopping point: if the camera cannot answer the original question, ask for the accessible findings and the proposed next step instead of an unsupported 'all clear'. Keep the investigation quotation separate from a replacement proposal so you can consider the evidence first. No fixed soakaway-survey price is given here because those scopes are not interchangeable.

Sources: DASA; Approved Document H.

• Is this definitely rainwater drainage rather than a sewage drainage field?
• Which pipe lengths and access points are included?
• Will the receiving system be assessed or only its inlet pipe?
• What information is needed about rainfall and previous work?
• Who decides whether ground investigation or infiltration testing is necessary?
• What evidence would justify repair or replacement?
• Which access, excavation and reinstatement costs remain unpriced?

Find and check a drainage contractor when you are ready to ask for quotes.