Though it isn’t one of the most glamorous parts of a house, the drain- waste-vent (DWV) system is one of the most necessary. The job of the drain-waste part of the system is to carry away waste water and sewage from sinks, bathtubs, showers, toilets, and water-using appliances such as dishwashers and washing machines, and to deliver those wastes to the septic tank or public sewer.

The vent system—part of the plumbing that is usually less well known to most homeowners—is connected to the drain-waste piping and its job is to ventilate sewage gases so they don’t build up in the house. The vent system also helps drain pipes maintain the right pressure for proper drainage.

The pipes of the DWV system are usually out of sight, hidden in the walls, beneath the floors, and in the attic. But when the system ceases to do its job properly, it is hardly out of mind. Clogged drains are among the most common problems that occur in a DWV system.

This section of HomeTips will help you understand how this all-important system works and what to do when it doesn’t.