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What is a vent and what does it do?

Vents are the pipes (about 12” high) that stick out of your roof. Vents are necessary to vent sewer gasses outside of the home. You can think of a vent pipe like a straw. When you put your thumb over the end of a straw, you can pull liquid up from the cup. What happens when you remove your thumb? The liquid drains out and the straw fills with air. Similarly, when liquid goes down a pipe, air needs to follow it. This air is pulled from the vent pipe. Without a vent pipe, the liquid will try to pull air through the P-traps on plumbing fixtures such as your tub and sink! If this happens, you’ll know from the smell! Likewise, without a vent, draining one fixture may cause another fixture in the house to back up!