Which system seals the trap that prevents sewer gases from entering homes?

To address the question about which system seals the trap that prevents sewer gases from entering homes, the P-trap is indeed the correct choice. The P-trap is a plumbing component that is installed beneath sinks, tubs, and other drainage fixtures. It has a distinctive shape that resembles the letter "P" and holds a small amount of water at all times. This water acts as a barrier, creating a seal that effectively prevents harmful sewer gases from escaping into the home.

While air gap systems and backflow preventers serve important functions in plumbing, they do not specifically function to seal out sewer gases in the same way that a P-trap does. An air gap provides a physical separation to prevent backflow, while a backflow preventer stops water from reversing direction in the system. However, neither of these systems is designed to hold water and create a gas barrier in the way that a P-trap does.

Therefore, it's clear that the P-trap plays a crucial role in plumbing systems by ensuring a safe and sanitary environment within homes.