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 this 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 less known to many homeowners--is connected to the drain-waste piping but has a different job. Its task is to ventilate sewage gasses so they don't build up in the house and so the drain pipes maintain the right pressure for proper drainage.

The pipes of the DWV system are usually out of sight and out of mind because they’re hidden in the walls, beneath the floor, and in the attic. But when the system ceases to do its job properly, it becomes painfully evident. Clogged drains are among the most common problems that occur in a house.

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