How does Drain Plumbing work?

When you pour liquid from a can, you’ll notice that it doesn’t flow evenly unless you have a second opening for air. The same holds true for plumbing vent pipe. As water goes down a drain, air is needed to equalize the pressure in the drain line. This is the purpose of a venting system. If the drain lines in your home have poor venting, water rushing down the drains will pull water from nearby P-traps. Unfortunately, a clogged or missing vent is tough to fix, since it usually requires breaking into the walls to examine the drain system. Unless you have plumbing experience, this project is best left to a professional.