A waste pipe carries waste water from sinks, dishwashers, showers and other appliances where water is used. As this aspect of plumbing only transports water it can be narrow in diameter.
Waterflow piping is named as such because it is a plumbing application that is fitted to a water storage tank or cistern and leads outside the home or building to prevent overflow. It is fitted above the maximum desired fluid level. Therefore, if liquid starts to reach the height of the overflow pipe level, instead of rising any further it flows through the overflow pipe and outside of the building. Common mechanisms that have an overflow pipe include toilet cisterns, combination boilers and sinks and baths.