Colebrook-White pipe sizing to Water UK DCG / BS EN 752: capacity, self-cleansing velocity, cover and access-chamber checks for foul and surface-water sewers.
1
Design Parameters
2
Pipe Sizing
3
Velocity Checks
4
Depth & Cover
5
Manhole Spacing
6
Results
Step 1: Design Parameters
Design basis & system
Auto-set by system (DCG: 0.6 surface / 1.5 foul, all materials); editable for material-specific design.
Project Information
Pipe Material Selection i
Hydraulics use the Colebrook-White roughness ks set above (Water UK DCG uses a single ks per system for all materials). Material is recorded for the schedule.
Gradient Guidance: Minimum recommended gradient is typically 1:100 (1%) for self-cleansing. Steeper gradients (1:50) are preferred for small diameter pipes. Consult site topography and downstream levels.
Step 2: Pipe Sizing Calculation
Calculation Complete: Standard pipe sizes calculated using the Colebrook-White equation (Water UK DCG). Select a pipe size to proceed.
Diameter
Full-bore Capacity
Full-bore Velocity
Proportional Depth (d/D)
Velocity @ Design
Utilisation
Action
Click "Calculate" to size pipes based on your design parameters.
Step 3: Velocity Checks & BS EN 752 Compliance
BS EN 752:2017 / Water UK DCG Requirements: Self-cleansing velocity — foul ≥ 0.75 m/s at one-third depth; surface water ≥ 1.0 m/s full-bore. Maximum 3.0 m/s (erosion protection). Optimal range 1.0–2.0 m/s.
✓ Self-Cleansing Check
At pipe one-third full (d/D = 0.33): - m/s
✓ Erosion Check
At full bore: - m/s
✓ Optimal Range
At design flow: - m/s
Detailed Velocity Analysis
Velocity @ d/D = 1/3
- m/s
Velocity @ Design Flow
- m/s
Velocity @ Full Bore
- m/s
Proportional Water Depth in Pipe
Velocity analysis will appear after pipe selection.
Step 4: Depth & Cover Requirements
Depth Analysis
Cover Depth at Inlet
- m
Cover Depth at Outlet
- m
Pipe Length
- m
Actual Gradient
- (1:X)
Step 5: Manhole & Access Spacing
Access & chamber sizing follows the design basis, system, depth to invert and pipe size chosen above (Water UK DCG / Building Regs Part H). Values below are per-access-point requirements.
Maximum Spacing
- m
Access type
-
Required chamber
-
Basis / standard
-
Access points & layout
Manhole spacing will be calculated based on selected pipe.
Step 6: Results & Compliance Summary
Recommended Design
Pipe Material
-
Pipe Diameter
- mm
Design Flow Rate
- l/s
Method / roughness
-
Flow Characteristics
Full-bore Capacity
- l/s
Design Flow Velocity
- m/s
Proportional Depth (d/D)
-
Capacity Utilisation
-
BS EN 752:2017 Compliance
✓ Self-Cleansing
V ≥ 0.75 m/s at d/D = 1/3 (pipe one-third full)
✓ Erosion Protection
V ≤ 3.0 m/s at full bore
✓ Optimal Velocity
1.0-2.0 m/s at design flow
✓ Gradient
Adequate for flow conveyance
✓ Capacity
Design flow within pipe capacity
Water UK Design & Construction Guidance (DCG, formerly Sewers for Adoption)
✓ Pipe Material
Approved for adoption
✓ Cover Depth
-
✓ Access Spacing
-
✓ Minimum Diameter
Pipe diameter ≥ 150mm
Network Summary
Complete the design: enter your design flow and finish the depth/cover step so the tool can judge compliance.
References: Colebrook-White transitional law; roughness k_s per HR Wallingford Tables for the Hydraulic Design of Pipes, Sewers & Channels / Water UK DCG (foul 1.5 mm, surface 0.6 mm); pipe sizing per BS EN 752:2017