The correct answer is D. All the above.
Sewer pipes are designed to carry wastewater away from homes and businesses to a treatment plant. The size of the pipe is determined by the amount of wastewater that needs to be carried. Pipes that are less than 0.4 m in diameter are designed to run full at maximum discharge. This means that the pipe is filled with wastewater at all times. Pipes that are greater than 0.4 m in diameter are designed to run ${\frac{2}{3}^{{\text{rd}}}}$ or ${\frac{3}{4}^{{\text{th}}}}$ full at maximum discharge. This means that the pipe is only filled with wastewater two-thirds or three-quarters of the way up. The minimum design velocity of sewer pipes is taken as 0.8 m/sec. This means that the wastewater should flow through the pipe at a speed of at least 0.8 m/sec. This helps to prevent the build-up of solids in the pipe.
The following are some of the reasons why it is important to design sewer pipes correctly:
- To prevent flooding: If sewer pipes are not designed correctly, they can become overloaded and overflow. This can lead to flooding in homes and businesses.
- To prevent the spread of disease: Sewer pipes can carry bacteria and viruses that can cause disease. If sewer pipes are not designed correctly, these bacteria and viruses can be released into the environment and cause illness.
- To protect the environment: Sewer pipes can carry pollutants that can damage the environment. If sewer pipes are not designed correctly, these pollutants can be released into the environment and cause harm.
It is important to hire a qualified engineer to design sewer pipes. The engineer will be able to determine the correct size and type of pipe for the job. The engineer will also be able to ensure that the pipe is designed to meet all of the necessary codes and regulations.