Do I need to glue aluminium foil on top of the heating cable?
The aluminium foil tape has to be glued on top of the cable to give maximum heat to the pipe.
If you install the heating cable on a metal pipe, a cable goes along the pipe, and an aluminium tape has to be glued on top.
In case you install the heating cable on a plastic pipe. An adhesive aluminium tape is glued first along the pipe; later the heating cable is traced by fixing it with adhesive aluminium tape on top.