Building materials, pipes, tubes, valves, taps, stop cocks, pipe fittings, manhole covers, gratings, tanks, drainage traps, drainage chambers; all being principally or wholly or metal and all included in class 6

Pipes, valves, man-hole covers, gratings, tanks, drainage traps except plastic drainage traps, drainage chambers; building materials excluding door casings, door frames and door panels; all being wholly or principally non-metallic and included in class 19