# Manhole schedule checker

> Check a connected manhole schedule for duplicate references, missing links, impossible depths, level runs, backfalls and calculated pipe gradients.

- Canonical HTML: https://rospower.co.uk/resources/manhole-schedule-checker/
- Documentation index: https://rospower.co.uk/llms.txt
- Updated: 2026-09-11

> This Markdown version contains the published explanatory content. Use the canonical HTML page for calculators, builders and other interactive controls.

## Page content

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

1. 1**Confirm direction and datum**Identify the intended flow direction and make sure every level is tied to the same project datum and drawing revision.
2. 2**Keep connections explicit**Enter the next chamber reference and the horizontal length for each connected outgoing run. Leave both blank at a genuine schedule endpoint.
3. 3**Review every warning**A backfall may be a typing error, a reversed direction or a real design issue. Correct the controlled schedule, not just this browser copy.
4. 4**Check the physical route**Arithmetic does not prove clearance, cover, chamber suitability, service coordination, buildability, condition or hydraulic performance.

## Sources and further guidance

- [Approved Document H](https://www.gov.uk/government/publications/drainage-and-waste-disposal-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](https://www.water.org.uk/sewerage-sector-guidance-approved-documents): Water UK publishes the Design and Construction Guidance and minimum information for adoptable sewer proposals.
- [BS EN 1610:2015](https://knowledge.bsigroup.com/products/construction-and-testing-of-drains-and-sewers): construction and testing of drains and sewers (BSI).
- [Excavation safety and inspection](https://www.hse.gov.uk/construction/safetytopics/excavations.htm): HSE guidance on support, access, underground services and inspection.

Related resources

- [Drainage invert level calculator](https://rospower.co.uk/resources/drainage-invert-level-calculator/)
- [Drainage gradients and falls](https://rospower.co.uk/resources/drainage-gradients/)
- [Pipe bedding and trench calculator](https://rospower.co.uk/resources/pipe-bedding-calculator/)
- [Underground services safe digging](https://rospower.co.uk/resources/underground-services-safe-digging/)
- [Drainage CCTV survey brief](https://rospower.co.uk/blog/drainage-cctv-survey-brief/)