Back Drop Junctions are needed when connection between lines of different elevations is required. Back Drop connections can be constructed either by using a regular 45° (Y) or 90° (T) junction in connection with an (M-seal) or by using a tumbling bay junction as shown below. CPC Back vitrified clay back drop connections are available in different sizes from DN 150 mm to DN 600 mm in both classes SS and ES series.