Drainage Pipe Slope Calculator
Minimum slope for self-cleansing velocity in a drain of given size and flow.
Rules of thumb match the math: 110 mm house drains lay at ~1:60–1:80. Too steep is also bad — liquids outrun solids.
Formula
Drainage Pipe Slope Calculator is a free drain pipe slope for process, mechanical and water engineers — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Drainage Pipe Slope Calculator
Minimum slope for self-cleansing velocity in a drain of given size and flow. The calculation implements S = (V·n / R^⅔)² (Manning, full-flow R = D/4) (BS EN 752 / CPHEEO sewerage manual). Rules of thumb match the math: 110 mm house drains lay at ~1:60–1:80. Too steep is also bad — liquids outrun solids.
How to use Drainage Pipe Slope Calculator
- 1Enter Pipe diameter in mm.
- 2Enter Target velocity in m/s (Self-cleansing ≥ 0.6 m/s).
- 3Enter Manning n.
- 4Read Required slope, Slope as 1 in N, Fall per 3 m length instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Drainage Pipe Slope Calculator?
- ✓Implements the standard formula — S = (V·n / R^⅔)² (Manning, full-flow R = D/4)
- ✓Reference cited on-page: BS EN 752 / CPHEEO sewerage manual
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Live worked example: the substitution recomputes from your numbers
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Drainage Pipe Slope Calculator use?+
It computes S = (V·n / R^⅔)² (Manning, full-flow R = D/4), per BS EN 752 / CPHEEO sewerage manual. The formula is displayed under the result along with a worked example substituted with your own inputs.
What should I keep in mind when using this calculator?+
Rules of thumb match the math: 110 mm house drains lay at ~1:60–1:80. Too steep is also bad — liquids outrun solids.
Does this work for any fluid?+
Yes — density and viscosity are inputs (with common fluids suggested in the field hints), so the same physics applies to water, oils, gases and process fluids. Compute always runs in SI internally, so unit mix-ups can't corrupt the result.
Is the Drainage Pipe Slope Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
Related Engineering tools
Reynolds Number Calculator
Compute Re from density, velocity, pipe diameter and viscosity — with instant laminar/turbulent classification.
● LiveLaminar vs Turbulent Flow Classifier
Classify hydraulic-oil or process-fluid flow regime from kinematic viscosity, line velocity and tube bore.
● LiveBernoulli Equation Solver
Solve downstream pressure between two points from velocities, elevations and fluid density (ideal, lossless).
● Live