Manhole schedule checker
Check chamber references, connections, cover and invert levels, depth, fall and gradient across a proposed drainage schedule.
Cover level is the stated level at the top of the chamber. Invert level is the level at the lowest internal point of the pipe. A connected run falls when the upstream outgoing invert is higher than the downstream incoming invert.
This checker validates arithmetic and internal consistency only. It does not select pipe sizes or gradients, model hydraulic capacity, design chambers, confirm cover requirements or establish adoption compliance.
Check a connected schedule
Enter each chamber once. Connect its outgoing pipe to the next chamber reference and provide that next chamber's incoming invert.
Chambers
3
Connected runs checked
2
Issues
0
| Chamber | Cover level (m) | Incoming invert (m) | Outgoing invert (m) | Pipe (mm) | Connects to | Run length (m) | Depth | Chamber drop | Run fall | Gradient | Status | Action |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1.600 m | Start | 300 mm | 1 in 100 | Checked | ||||||||
| 1.650 m | 50 mm | 250 mm | 1 in 100 | Checked | ||||||||
| 1.700 m | 50 mm | End | End | Checked |
Example schedule checked. Edit any value to recalculate. Nothing is uploaded or stored.
How each check works
Chamber depth
Cover level minus outgoing invert level. The result is a schedule check, not a structural chamber depth or access classification.
Drop through the chamber
Incoming invert minus outgoing invert. A negative result means the stated outgoing invert rises through the chamber and needs review.
Run fall
Current outgoing invert minus the next chamber's incoming invert. Zero is a level run; a negative value is a backfall in the stated direction.
Calculated gradient
Horizontal run length divided by positive fall. The checker reports the geometry as 1 in N but does not decide whether that gradient is suitable.
Reference and connection
Every chamber reference must be unique. Each stated downstream connection must point to another chamber in the working schedule.
Pipe diameter
The diameter is carried into the exported check for coordination. No sizing, capacity or change-of-diameter rule is applied.
Use the schedule safely
- 1Confirm direction and datumIdentify the intended flow direction and make sure every level is tied to the same project datum and drawing revision.
- 2Keep connections explicitEnter the next chamber reference and the horizontal length for each connected outgoing run. Leave both blank at a genuine schedule endpoint.
- 3Review every warningA backfall may be a typing error, a reversed direction or a real design issue. Correct the controlled schedule, not just this browser copy.
- 4Check the physical routeArithmetic does not prove clearance, cover, chamber suitability, service coordination, buildability, condition or hydraulic performance.
Sources and further guidance
- Approved Document H: current Building Regulations guidance for foul and surface water drainage in England, including manholes and inspection chambers.
- Sewerage Sector Guidance approved documents: Water UK publishes the Design and Construction Guidance and minimum information for adoptable sewer proposals.
- BS EN 1610:2015: construction and testing of drains and sewers (BSI).
- Excavation safety and inspection: HSE guidance on support, access, underground services and inspection.
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