Most People Fail This Plumbing Quiz — Can You Pass?
You need to prevent backflow in a sink drain. Which part is correct?
Correct Incorrect A P-trap holds water to block sewer gases and prevent backflow. If it dries out, odors can enter the home, which is why pouring a small amount of water into unused drains is important. Some people assume valves alone prevent backflow, but only the water seal in a trap creates a proper barrier.