Most toilets and sinks are fitted with ABS or plastic flanges, a closet flange that sits beneath the fixture, near the bathroom floor or a drain pipe. As water flows into your toilet bowl, it fills up this section of piping until the volume of water exceeds the pipe's capacity. The excess spills over the top of your flange, flowing down to your drainage pipes in your walls. This is why you'll often see decorative "spouts" coming out from the wall beside each plumbing fixture, they direct excess water so it can flow harmlessly away from your home's foundation instead of around it.