Final answer:
In engineering, an additional circuit vent must be installed when there are issues with the drainage system. A circuit vent helps maintain proper water flow by allowing air to enter the drain pipe. It can be especially useful in case of blockages.
Step-by-step explanation:
In the field of engineering, an additional circuit vent must be installed whenever there are problems with the drainage system in a building.
A circuit vent is a vertical pipe that connects to the drain pipe and allows air to enter, preventing negative pressure and ensuring the proper flow of water.
For example, if there is a blockage in the drain pipe, the circuit vent can help release the trapped air and allow the water to flow smoothly.