When you are making plumbing repairs, it makes a big difference if you understand how the plumbing system works. It’s difficult to know because the plumbing is hidden behind the walls and under the floors. A standard residential home plumbing system is made up of three systems: water supply system, the water drain-waste system, and the water vent system.
Diagram of a typical residential plumbing system - Supply, drain, and venting systems.
The residential water supply system transports pressurized water from the water utility company (or a well on the property) into the house and all the way to the sink, toilet, bath tub, and other water using appliances such as the dishwasher and washing machine.
The residential water drain-waste system delivers used water and solid waste out of the house and into the sewer system or septic tank.
The residential water vent system transports noxious sewer gases away from the house and maintains appropriate pressure inside the drainpipes, also preventing the sewer gases from entering the house.