The correct answer is D. All the above.
Sewer ventilating columns are generally placed at distances of 150 m to 300 m, at the upper ends of branch sewers, and at every change in the size of sewers.
Sewer ventilating columns are used to provide ventilation to sewer systems. They help to prevent the build-up of gases and odors in sewers, and they also help to prevent the spread of disease.
Sewer ventilating columns are typically made of concrete or steel, and they are usually cylindrical in shape. They are typically installed at ground level, and they may be capped with a grating or a screen.
Sewer ventilating columns are an important part of sewer systems, and they help to keep our communities safe and healthy.
Here are some additional details about each of the options:
- Option A: Distances 150 m to 300 m
Sewer ventilating columns are typically placed at distances of 150 m to 300 m. This is because this is the distance at which sewer gases can build up to dangerous levels.
- Option B: Upper ends of branch sewers
Sewer ventilating columns are also typically placed at the upper ends of branch sewers. This is because branch sewers are more likely to have sewer gases build up than main sewers.
- Option C: Every change in the size of sewers
Sewer ventilating columns are also typically placed at every change in the size of sewers. This is because changes in the size of sewers can create areas where sewer gases can build up.