Heat cable belongs on a water pipe that is exposed to freezing and cannot be kept warm any other way: the water entry in the crawlspace, the section between the pump and the tank in a cold area, or a pipe running along an outside wall. It is laid along the pipe, plugged into a GFCI-protected outlet and installed strictly according to the manufacturer's instructions. Here is what we check at Wilfrid David in Chénéville when we inspect a heat cable at a cottage or home in La Petite-Nation.
Where heat cable belongs
The right location is an exposed water pipe in an unheated space: the crawlspace, the garage, the line rising through the floor to the pump, or the piping under a cottage built on posts.
Pipe heat cable should not be installed inside a wall, floor or ceiling; one manufacturer's guide prohibits this explicitly. It is designed for the pipe only and should not be wrapped around anything else to use up extra length.
It is also worth noting that if the buried line between the well and the building freezes every winter, a cable installed in the crawlspace will not solve the problem. The cause lies in the depth or insulation of that line, not in the visible section.
Two types of cable, two sets of rules
There are two main families of heat cable, and a practice that is acceptable with one can be dangerous with the other.
Constant-wattage cable produces the same amount of heat whenever it is on and usually has a thermostat attached to the pipe. One Québec manufacturer's guide is precise: the cable must never touch, cross or overlap itself; it must not be spiralled around the pipe or cut; and it must not be installed on plastic pipe unless that pipe is full of water at all times. Otherwise, the cable can overheat, creating a risk of fire or electric shock.
Self-regulating cable adjusts its own heat output to the temperature. Another Québec manufacturer states that its cable may overlap during installation and is suitable for both metal and plastic pipe. It recommends applying aluminum foil to plastic pipe so that heat spreads more evenly.
Insulation requirements also vary: one guide calls for at least 1/2 inch of fibreglass over the cable, while another sets a maximum of 1/2 inch. This is why it is essential to follow the instructions for your own cable. As a general rule, no insulation should cover a cable unless the manufacturer allows it, and in that case it must be a non-combustible material such as fibreglass.
On a horizontal pipe, the cable is usually laid along the underside and secured with fibreglass or aluminum tape. Ordinary electrical tape is not recommended, as it can let the cable slip. Keep the box and the instructions near the electrical panel for future reference.
Electrical precautions
Always switch off the power before handling the cable.
Plug it into an outlet protected by a ground fault circuit interrupter (GFCI). One manufacturer requires this; the other strongly recommends it and explains why: a damaged cable can leak enough current to be dangerous without tripping a standard breaker.
If there is no outlet near the pipe, adding one is a job for an electrician. This is far preferable to an extension cord left in the crawlspace all winter.
How to tell if it is working
A cable with a thermostat does not heat continuously. The one described in one of the guides switches on when its thermostat senses about 3 °C and switches off once the pipe reaches about 10 °C. A cable that feels cold on a mild autumn day is therefore normal; it should be assessed in cold weather.
If the plug or cable has an indicator light, check it. For its self-regulating cable, one manufacturer suggests a simple test: one hour after plugging it in, open the tap and confirm that the water coming out is lukewarm.
If the GFCI trips, do not keep resetting it. A trip indicates a current leak, often from the cable itself.
Inspect the cable visually as well, with the power off. One of the guides calls for an inspection at the start of the season and then monthly while the cable is in use. A cracked jacket, black marks, exposed wires or sections chewed by rodents mean the cable must be unplugged and replaced. Any old heat tape still attached to the pipe should be removed before a new cable is installed.
When to call a professional
If a pipe freezes despite the cable, the GFCI keeps tripping, the cable is damaged or you are unsure which type you have, call us at 819-428-3161. We will inspect the installation, thaw the line if needed and advise whether heat cable is the right solution. If the pipe is already frozen, start with our article on thawing frozen pipes safely. If the whole cottage is without water, see what to check when there is no water. For more information, visit our pipe thawing and heat cable page.
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