The drain pipe is the piece that carries the waste out of the bowl and into the main plumbing system. The drain pipe is usually made of PVC instead of metal, for more effective drainage. This part interacts closest with the tank and the bowl. As the tank’s water supply flows down into the bowl once the handle has been pulled, the rush of water causes the bowl to drain down into the drain pipe, sending waste out of the toilet and into the sewage pipes.

Most toilets have a three-inch diameter pipe, but some go as high as four and a half inches, depending on the drainage type and amount. Some toilets even offer two-inch drainage pipes; however, these aren’t recommended as they tend to slow drainage and break much easier. These pipes are the most crucial and expensive repair in the toilet, as a broken or busted pipe can cause gallons of water to flood into the walls, flooring, or ceiling below the toilet, leaving costly plumbing and flooring/ceiling repairs.