There are two major types of drains in the average home: primary drains and secondary drains. Secondary drains are visible under sinks, floors, and behind walls. There is also a distinction between waste pipes and drainpipes. Waste pipes are specific to toilets, while drainpipes carry greywater from sinks, appliances, showers, and bathtubs. All drains in a house lead ultimately to the municipal sewer where it is transported to the water treatment plant.