Wintecs have this to say about it...
The heating cable must not touch, cross or overlap itself at any point. This will cause the heating cable to overheat.
The heating cable cannot be altered in length. If made shorter, it will overheat and if made longer, it will produce insufficient heat. Any attempt to physically alter the heating cable will void the warranty. Once cut, the heating cable cannot be repaired
If you are applying the heating cable to a plastic hose, it is recommend that you first wrap the pipe with aluminum foil before applying the heating cable. The aluminum foil distributes the heat from the heating cable uniformly around the pipe, as aluminum is a better heat conductor than plastic.
Using a good quality PVC electrical tape, lay the heating cable on the pipe and fasten it to the pipe at approximately 600 mm intervals.
For hose freeze protection under extremely cold conditions, or for minimizing energy consump-tion, it is recommended that insulation be added to the hose over the heating cable. The heating cable/hose may be insulated with either fibreglass or polyethylene foam insulation.