Ventilation

The ventilation of sewers (Figure 13) is desirable to prevent the accumulation of dangerous explosive or corrosive gases; the concentration of unpleasant odours that may escape to cause a nuisance in the environment; accumulation of hydrogen sulphide, which corrodes concrete and metal exposed to it in the sewer and in the, plumbing; and, the creation of pressures (above or below atmospheric) that may break water seal in plumbing traps. Pressures in the system are developed by the wind blowing up the outlet; and, also by the trapping of air due to surcharge of sewer; and due to other causes as well.

                                Figure 13: A Ventilating Column Connected to a Sewer