Garden SurveyorDrainage Calculator
French drains, channel drains, soakaway crates, land drains and patio falls.
2 advanced inputs hidden. Switch to Advanced to fine-tune.
- Run length
- 10m
- Drainage type
- french-drain
- Perforated pipe
- 10m
- Drainage gravel
- 1.8t
- Geotextile membrane
- 15m²
Heads-up: Pipe falls matter more than pipe size: 1:80 minimum for foul, 1:40 for shallow surface runs. Too shallow and it silts; too steep and water runs ahead of solids. Why it matters: Connecting to a public sewer needs a Section 106 approval from your water authority.
Underground services check recommended before excavation. Use a CAT scanner or contact utility providers.
Why it matters: Gas, electric, water and telecoms cables are often shallower than expected — HSE guidance HSG47 mandates a safe-digging process.
If ignored: Striking a live service can cause serious injury, supply outages affecting the whole street, and personal liability for repair costs.
This app provides general UK guidance and material estimates only. It is not legal, planning, engineering or building-control advice. Always confirm requirements with your local planning authority, building control, utility providers, manufacturers or qualified professionals.