YS-INF-SW-01

SEWER PIPE DESIGN

Problem

Design 90m sewer pipe that meant to carry 120,000PE. The start and end nodes invert level are controlled at 1.00m and 0.90m respectively.

Solution

1. Determine peak flow factor by referring to cl.2.1.14(II) MSIG Vol. 3.
2. Calculate the design flow by multiplying peak flow factor to design PE, which equals to 225L/s.
3. Determine the gradient of pipeline by dividing pipe length using invert level difference.
4. Set sewer pipe diameter, subjected to the minimum of 225mm, as stated in cl.2.1.17, MSIG Vol. 3. 
5. Determine the pipe material.
6. Determine Hazen-Williams coefficient based on Table 2.4, MSIG Vol. 3.
7. Calculate full pipe flow velocity using Hazen-Williams equation, referring to cl.2.1.17(3), MSIG Vol. 3.
8. Determine Manning's coefficient based on Table 2.3, MSIG Vol. 3, for the best and worst conditions.
9. Calculate full pipe flow velocity using Manning's equation, referring to cl.2.1.17(2), MSIG Vol. 3 for both conditions.
10. Determine roughness coefficient based on Table 2.1a & Table 2.2, MSIG Vol. 3, for the best and worst conditions.
11. Calculate full pipe flow velocity using Colebrook-White equation, referring to cl.2.1.17(1), MSIG Vol. 3 for both conditions.
12. Calculate full pipe capacity by multiplying pipe cross sectional area to full pipe flow velocity.
13. Check whether the velocity through sewer pipe lies between 0.8m/s to 4.0m/s, which is the acceptable range based on cl.2.1.15(I) and cl.2.1.17, MSIG Vol. 3.
14. Calculate the design flow to pipe capacity ratio.