Final answer:
The purpose of an air gap between the faucet and the flood rim of a three compartment sink is to prevent the backflow of contaminated water into the potable water supply and to allow for effective drainage.
Step-by-step explanation:
The purpose of an air gap between the faucet and the flood rim of a three compartment sink is to prevent backflow of contaminated water into the potable water supply. The air gap acts as a physical barrier that prevents any cross-contamination between the two water sources.
When there is a sudden drop in pressure in the potable water supply, such as during a water main break or high water demand, the air gap ensures that contaminated water from the sink cannot be siphoned back into the water supply. This protects the public's health by preventing the spread of harmful bacteria or chemicals.
Additionally, the air gap allows for effective drainage and prevents any potential overflow or flooding of the sink. The gap provides a space for water to exit freely and prevents any blockages that could occur if the sink were to be completely sealed.