Heat Tape for Pipes

Heat tape — heat trace cable, if you want the technical name — is a flexible electrical element that keeps water pipes from freezing. Electric heat tracing uses heat tracing cables to maintain or raise the temperature of pipes and vessels, with the heating element in contact with the pipe, typically covered with thermal insulation to retain heat and reduce losses. The cable replaces heat lost through insulation, holding the pipe and its contents above freezing.

For broader project planning, explore WBC’s building materials resources.

For a Montana water line — well house, crawlspace run, exposed supply pipe on a north wall — the single most important decision is matching the cable type to your pipe material. Get that wrong and you’re not just risking a frozen pipe. You’re risking a fire.

Here’s the short version. If your water supply piping is plastic, ONLY use automatic thermostatically controlled heat tape. Non-automatic heat tapes can damage plastic pipes, especially if the taped pipes are covered with insulation. That’s the rule that matters most.

How Heat Tape Actually Works

The principle is simple. Every pipe loses heat when it’s warmer than the air around it. Thermal insulation reduces the rate of heat loss but does not eliminate it. Trace heating maintains the temperature above freezing by balancing heat lost with heat supplied.

A thermostat handles the cycling. Normally a thermostat energizes when it measures temperature falling below a set value — usually between 3°C and 5°C, the ‘setpoint’ — and de-energizes when temperature rises past another value, usually 2°C higher. So the cable isn’t running full-blast around the clock. It kicks on when the cold demands it.

An electric heating cable system uses the cable to replace the heat lost through the thermal insulation. Replacing that lost heat keeps the pipe and fluid at a constant temperature — keeping water from freezing and bursting a pipe, or a liquid from congealing and plugging it.

Freeze protection is the bread-and-butter use, but the same cable family handles other jobs. Applications include freeze protection, maintaining flow temperature in hot water systems, and ensuring process temperatures for substances that solidify at ambient temperatures. Roof and gutter de-icing is common too — cable placed in gutters isn’t meant to keep them ice-free, but to provide a free path for melted water to get off the roof and down the downspout.

The Three Cable Types — and Why Self-Regulating Wins for Homes

There are three families here, and they’re not interchangeable.

Self-regulating is the one to reach for on a house. Self-regulating cables adjust heat output automatically in response to heat loss along the entire circuit. When ambient temperature drops, the cable increases its output. When temperature rises, output decreases. The cable does the thinking for you, section by section. Different self-regulating cables range in maintain temperature from 65°C (150°F) to 200°C (392°F).

The big safety advantage shows up on dry pipe. A product like Paladin demonstrates what good self-regulating cable does — it increases heat output to cold sections while reducing output to warm sections, so you never have to worry about the system overheating, melting, or causing fire. It’s rated to provide reliable freeze protection of both metallic and non-metallic pipes. Paladin also carries direct earth burial and wet location approvals — which matters when you’re running a line below grade to the frost depth, exactly the situation across western Montana.

Constant wattage puts out steady heat regardless of conditions. The benefit over series cable is that if one small element fails, the rest keeps operating — but damaged sections (usually a 3-foot span) stay cold and can lead to freeze-ups on that section. It always needs a thermostat for reliable control, and it’s the type you must never overlap or cross.

Series cable is the industrial option, and not what you want on a residential line. If series cables are crossed over themselves they can overheat and burn out, they come in specific lengths and cannot be shortened in the field, and a break anywhere along the line fails the entire cable. It’s a run of high-resistance wire, insulated and often jacketed. Built for long pipelines, not your well house.

One more thing worth flagging. The term “self-regulating heat tape” can be misleading — what’s sold as heating tape is most often constant wattage, operating at a fixed output regardless of surrounding temperature, which can lead to dangerous overheating or melting of the pipe. Read the label, not the shelf tag.

Cable type	Output behavior	Plastic pipe?	Overlap allowed?	Cut to length?	Best for
Self-regulating	Adjusts by section to temperature	Yes (rated types)	Yes, on cable rated for it (e.g. Paladin)	Yes (parallel construction)	Residential water lines, well houses, barns
Constant wattage	Steady output, needs thermostat	Often metal only	No — overheat/fire risk	Yes, in field	Metal pipe runs
Series	Fixed output, single power feed	No	No	No — fixed lengths only	Long industrial pipelines

Matching Cable to Pipe — the Safety Line You Don’t Cross

This is where the fires come from. Heat tape goes on all exterior water supply piping and shutoff valves, plus any interior pipes running along outside walls where temperature may drop below freezing. On a Montana manufactured home, seasonal cabin, or unheated crawlspace, that’s a lot of pipe.

If that pipe is plastic — PVC or PEX — only automatic, thermostatically controlled cable touches it. The danger isn’t theoretical. If you don’t check your heat tape regularly, it can deteriorate to the point that it actually melts plastic pipe, which has led to fire and water damage in homes. And many manufactured home fires are the result of improperly installed heat tape. Montana has a lot of manufactured and seasonal homes. This message is for them especially.

Self-regulating cable sidesteps the melt risk by design. The Paladin example again: you never have to worry about it overheating, melting, or causing fire because of the self-regulating technology. When in doubt about a specific cable on a specific pipe, the manufacturer’s application guide is the final word — installation on plastic pipe requires special considerations in selection and installation; refer to the cable Application Guide for design and selection details.

Installation Basics

The cable runs the full length of the line. Start with the plug end next to the outlet and run the heat tape the entire length of the freshwater supply pipe. Also wrap the pipe below ground level, to the frost level. In western Montana, frost runs 36 to 48 inches — so that buried portion is real, and the cable has to reach it.

Secure it along the bottom of the pipe — the 5 or 7 o’clock position — and hold it with fiberglass tape or UV-resistant ties. Use electrical tape, not electrical wire, to hold the heat tape in place.

The cardinal sins, all of them fire hazards:

• Do not cross the heat tape back over itself — this could overheat the tape and start a fire. The exception is cable specifically rated for overlap; Paladin, for one, can be overlapped without the concern of overheating.
• Do not overlap heat tape over itself, and do not wrap tape at a 90-degree bend.
• Do not use an extension cord. The heat tape must plug directly into a Ground Fault Circuit Interrupter (GFCI) receptacle.

Insulate over the cable once it’s secured. Cover the pipe and heat tape with pipe insulation or jacketing; if the insulation doesn’t have a weather-protective outer surface, cover it with a waterproof wrap. That insulation isn’t optional in this climate — it’s what makes the system efficient. With a self-regulating system, adding thermal insulation and a thermostat can increase energy efficiency by as much as 80%.

One nuance on insulation placement: the manufactured-home guidance warns against running heat tape over existing thermal insulation or near flammable material. The cable goes on the bare pipe, then insulation goes over the assembly. Don’t sandwich it the wrong way.

Then check it every year. When checking heat tapes at least once a year, pay particular attention to older tape, which may develop cracks in the insulation. Cracked or frayed cable gets replaced — with the correct size for the job.

Sizing and How Much to Buy

Buy by the pipe, not by guesswork. How much you need depends on the length, size, and type of pipe — you need the pipe length and diameter and the number of valves or faucets along the run. To determine the amount, consult the manufacturer’s guidelines.

A good self-regulating system can save you cable. Where traditional hardware-store heat tape must be spiraled around the pipe to apply adequate heat, Paladin is applied in a single straight run in most applications — reducing the overall length of product needed by as much as 60%. Spiraling is still the move when you need more heat density on a larger pipe or in extreme cold.

Cut-to-length cables give you flexibility. The DEVIpipeheat 10 V2, a self-limiting cable, is one example: twin conductor, cut-to-length, with 10W/m output at 10°C on 230V supply. Its minimum bend diameter is 50mm, operating temperature tops out at 65°C, and it carries an IP68 rating with a 5-year warranty. Series cable, by contrast, can’t be shortened at all — another reason it’s a poor residential fit.

Western Building Center carries Easy Heat pre-terminated pipe heating cable in several fixed lengths — 3-foot, 9-foot, 15-foot, and 18-foot runs — along with fiberglass pipe insulation and roof heating cable clips. The pre-made lengths take the guesswork out of smaller jobs; match the run to your measured pipe and leave a little extra at connections.

Frequently Asked Questions

Can I put any heat tape on PEX or PVC pipe? No. Only automatic, thermostatically controlled — meaning self-regulating — cable should go on plastic pipe. Non-automatic heat tapes can damage plastic pipes, especially if the taped pipes are covered with insulation. Self-regulating cable rated for non-metallic pipe is the safe choice because it won’t overheat.

Does heat tape have to be plugged into a GFCI outlet? Yes, and directly. Do not use an extension cord — the heat tape must plug directly into a Ground Fault Circuit Interrupter (GFCI) receptacle. If there’s no GFCI outlet near the water inlet, one needs to be installed.

Why can’t I just overlap the cable to add more heat in a cold spot? Because on most cable that overheats and starts fires. Crossing the tape back over itself could overheat the tape and start a fire. The exception is cable specifically engineered for it — self-regulating cable like Paladin can be overlapped without the concern of overheating. If you need more heat on a stretch, spiral the cable per the manufacturer’s spacing, or step up to a higher-output product.

How far down the pipe does the cable need to go? All the way to the frost line. Run the heat tape the entire length of the freshwater supply pipe, and wrap the pipe below ground level to the frost level. Across most of western Montana that’s 36 to 48 inches deep, so plan your cable length to reach it.

Do I still need pipe insulation if I have heat tape? Yes. Insulation is what makes the heat tape efficient — it slows the heat loss the cable is fighting. Adding thermal insulation and a thermostat to a self-regulating system can increase energy efficiency by as much as 80%. Cover the cable with pipe insulation, then a waterproof wrap if the insulation isn’t weather-rated.

How often should I check it? At least once a year, before cold weather sets in. Check heat tapes at least once a year, paying particular attention to older tape, which may develop cracks in the insulation. Cracked or frayed cable gets replaced, not patched.