The amount of heat cable needed for pipe freeze prevention is determined by a couple of simple factors including: Length of pipe, diameter of pipe, distance to power supply and number of valves.
We do not recommend a spiral cable application mostly because it’s simply not necessary. It requires 3x the cable to do the same job.
Therefore, simply use a straight, single run of cable affixed to the bottom of the pipe (think 6 o’clock position) using the provided fiberglass installation tape. Next, add 1 foot of cable for every valve because you will be wrapping the valve with cable. For pipes less than 1″ in diameter, a single cable run is sufficient. For larger pipes, two cable runs are recommended. Keep in mind that plastic pipes are less thermally conductive so you may choose to use two cable runs on larger plastic pipes to be safe. Finally, if your outlet isn’t close to the pipe you are treating, factor in enough heat cable to reach your outlet (Pipe Freeze PRO does come with a 36″ power cord).
Finally, you must install insulation on your pipe and heat cable assembly in order for the system to operate effectively. See instructions for further details.