Tutorials CivilCraft help Walkthroughs
Work out sanitary design flows and check the sewer
Enter the people and area that enter at each manhole of a sanitary network; CivilCraft adds them up down the network, works out the peak flow with a peaking factor and infiltration, and checks each pipe's capacity and velocity.
Written for CivilCraft 0.6.1. The same help is inside the app: press F1.
Sanitary design flows work on the pipe network when its Type is Sanitary. With nothing selected, the right panel then shows Sanitary design flows where a storm network shows storm drainage.
Enter what comes in
- Select a manhole. Under Sanitary design flows, type the People entering here and the Area entering here (hectares in a metre project, acres in a feet project).
- For shops, offices or industry, type equivalent people: the area times the people per hectare (or acre) your agency uses. The area counts for infiltration either way.
- Repeat for each manhole where a street or a lot connects. A manhole where nothing connects keeps both at 0.
Each pipe carries everything that enters at its upper manhole and above it. Select a manhole to see what passes through it.
The settings
| Setting | What it means |
|---|---|
| Flow per person | the average flow of one person a day: litres (metre project) or US gallons (feet project) |
| Infiltration | groundwater that leaks in: litres per second per hectare, or gallons a day per acre |
| Peaking factor | Harmon, 1 + 14 / (4 + √P), or Babbitt, 5 / P^0.2, with P the population in thousands |
| Peaking factor at least / Peaking factor at most | the factor is held between these two |
| Manning n | for capacity and velocity |
| Least velocity / Most velocity | at the peak flow's own depth in the pipe |
| Most of full capacity | how full a pipe may run at the peak, as a percent of what it carries flowing full |
The starting values are placeholders, not a standard. Use the values your agency publishes.
What it works out
For each pipe, in flow order:
- peak flow = people × flow per person × peaking factor + area × infiltration
- capacity flowing full (Manning's equation at the pipe's slope), and how full the peak makes it
- the normal depth of the peak flow and the velocity there
The Sanitary results table lists each pipe's people, peaking factor, peak flow (L/s, or gpm and cubic feet per second), percent full and velocity. Problems are listed under it: a pipe fuller than the limit, slower than the least velocity (it may not clean itself), faster than the most, or with no fall. Size the pipes for these flows picks for each pipe the smallest standard size (200 mm or 8 inches and up) that carries its peak within the limit; one ⌘ZCtrl+Z undoes it.
Velocities use Manning's equation with the same n at every depth. Some agencies' part-full charts let n change with depth, which gives a slightly lower velocity in a pipe running 60 to 70 percent full (about 3 percent less).