Confidence votes 146. Wastewater from your kitchen and bathroom is piped to a gully trap before emptying into the sewer. A gully trap is a basin in the ground with a water seal to prevent foul odours of the sewer reaching the surface.Gully traps are buried in the ground with the tops or surround raised above ground level to prevent ground water entering into the sewer.he difference between a gully trap drain and a floor drain is  placement. A floor drain is in a floor, a gully trap drain goes on  an external wall. 4 people found this useful.