Winter work
Heat tape for pipes: what to install, where it belongs and how to quote it
Heat tape is a small job that can cause a fire when it's done wrong. Here is the difference between self-regulating and constant-wattage cable, where it makes sense and where insulation or a reroute is the better fix, the install rules from two manufacturers' instructions, a fall check, and what to put on the quote.
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The first cold snap brings the same calls: no water in the kitchen, a frozen line in the crawl space, a mobile home with a heat tape that stopped working. Heat tape looks like a parts-counter sale, but it's an electrical heater wrapped around a water pipe and buried under insulation, where nobody sees it fail.
This guide covers what heat tape is, the two kinds you'll find, where it's the right fix, the installation rules from the manufacturers' own instructions, the check to do each fall, and how to quote it. It ends with what to do about a pipe that has already frozen or burst.
The install rules below come from two sets of manufacturer instructions: Chemelex's Raychem FrostGuard 120 V cable (formerly sold under nVent) and Easy Heat's AHB and HB cables. Other products have different rules. Follow the instructions for the cable in your hand, your electrical code and your inspector.
What heat tape is
"Heat tape" is the everyday name for an electric heating cable fastened along a water pipe to keep it above freezing. Most residential products come pre-assembled: a heating section of fixed length, a power cord and a plug. FrostGuard 120 V, for example, comes in lengths from 6 to 100 feet with a 6-foot cord and a lighted plug that shows when the cable has power, and Chemelex pitches it for metal or plastic pipes up to 2-1/2 inches.
Self-regulating vs constant-wattage
| Self-regulating | Constant-wattage (fixed output) | |
|---|---|---|
| How it heats | Output drops as the pipe warms | Same output whenever it's on |
| Control | The cable itself (FrostGuard plugs straight into the outlet) | A built-in or separate thermostat, or someone watching it |
| Length | Extra cable can be spiraled or doubled back (FrostGuard) | Must match the pipe; never longer, never overlapped (Easy Heat) |
| Example | Raychem FrostGuard | Easy Heat AHB (built-in thermostat), Easy Heat HB (none) |
Chemelex's data sheet gives FrostGuard a nominal output of 6 watts per foot on a pipe at 40°F, and its curve falls as the pipe gets warmer. Easy Heat's AHB thermostat switches the cable on below 38°F and off once the pipe reaches about 45°F. Easy Heat's HB has no thermostat at all: its instructions say it must be controlled by a separate thermostat or by continuous monitoring, and require a switch with a pilot light or a thermostat on the supply.
The practical difference is overlap. A self-regulating cable turns itself down where it touches itself. A constant-wattage cable doesn't, so a crossed or coiled section keeps heating until something melts.
Where it makes sense
- Crawl spaces and unheated basements where a short run is exposed and can't easily be moved.
- Pipes on exterior walls, where they're accessible. FrostGuard's instructions say not to install it behind walls or anywhere the cable would be hidden.
- Mobile homes, where the supply riser is exposed under the home. Easy Heat's kit notes that many mobile home heat tape receptacles are not GFCI protected, so check the outlet before you plug anything in.
- Exposed well lines and pressure tank piping in a pump house or well pit that stays cold.
Where something else is better
- Inside walls, floors and ceilings. Both manufacturers say no. Open the wall and reroute or insulate instead.
- Buried lines. Easy Heat says its AHB cable must not be buried or touch the ground. A service line that keeps freezing needs to go deeper: Minneapolis tells owners whose line often freezes to have a contractor lower it to a depth frost can't reach.
- Drain, fuel and hose lines. Easy Heat's AHB is for water-filled supply pipes only, and FrostGuard can't be used on flexible vinyl tubing such as garden hoses.
- A cold space you can fix. Sealing the draft, insulating the run or heating the space removes the risk instead of managing it.
Installation rules from the instructions
Ground-fault protection
Chemelex's FrostGuard data sheet requires 30-mA equipment or 5-mA personnel ground-fault protection on each heating cable branch circuit, because arcing from a damaged cable may not be stopped by a regular breaker. Its install sheet lists a ground-fault protected outlet (GFCI) as required but not supplied. Easy Heat's HB instructions also require a ground fault protected circuit such as a GFCI receptacle; its AHB kit recommends one.
No overlap, and the right length
For constant-wattage cable, Easy Heat is blunt: never let the cable touch, cross or overlap itself, never use one cable on more than one pipe, and never use a cable longer than the pipe. The AHB is applied straight along the bottom of horizontal pipe, not spiraled. On the HB, spiral turns must be at least 1/2 inch apart. FrostGuard is different: add 1 foot of cable for each valve or spigot, and if the cable is longer than the pipe, spiral it evenly or double the excess back along the pipe.
Fastening
FrostGuard goes at the 4 or 8 o'clock position for straight runs, fastened every foot with fiberglass application tape or nylon ties. Chemelex says no vinyl electrical tape, duct tape, metal bands or wire. Easy Heat's AHB calls for its own application tape or electrical tape rated for at least 176°F.
Insulation over it
The two brands disagree on thickness, which is why you read the sheet. FrostGuard needs at least 1/2 inch of fire-resistant, waterproof insulation, such as preformed foam or fiberglass, and 1 inch for protection down to -20°F. Easy Heat's AHB calls for 1/2-inch fiberglass or another non-flammable pipe insulation and warns never to use more, because over-insulation can overheat the cable.
Plastic pipe
FrostGuard can be used on metal and plastic water pipe. Easy Heat's HB is for metal pipe only, outdoors only. Its AHB can go on plastic, PEX included, but only on pipe that is always full of water, and Easy Heat recommends wrapping plastic pipe in aluminum foil first for even heat.
Other rules worth knowing
- No extension cords with FrostGuard.
- Do the piping pressure test before you put the cable on (Chemelex).
- Never put the cable in or through walls, ceilings or floors (both brands).
- Put the "Electric Traced" labels on the outside of the insulation so the next plumber knows there's a cable under it (Chemelex).
- Leave the instructions with the owner (both brands).
Electrical safety
Chemelex's FrostGuard instructions say Articles 422 and 427 of the National Electrical Code govern its installation for pipe freeze protection. If the outlet isn't GFCI protected, or there's no outlet near the pipe, that's electrical work. Price an electrician unless you're licensed for it.
The Consumer Product Safety Commission's heat tape guidelines (reissued January 22, 1996) say much the same: use a three-prong plug in a three-prong outlet and a GFCI, don't wrap a tape over itself unless the maker allows it, keep end caps sealed and off the ground, don't use pipe tapes on gutters or fuel lines, and replace uncertified tapes more than three years old with certified ones.
Checking it each fall
Old heat tape is where the trouble is. A fall visit is a quick, useful service call:
- Look at the whole run. Easy Heat says to inspect the cable and its power connection at the start of the heating season and monthly while it's on, and to remove any cable that is cut, damaged, has been under water, or shows charring or cracking.
- Check the outlet. Test the GFCI. Make sure the plug is a grounded three-prong plug in a matching outlet.
- Megger it. Chemelex calls for an insulation resistance test with a 2,500-volt DC megohmmeter between the power prongs and the ground prong, with at least 1,000 megohms. Record the reading and compare each year. Below 1,000, replace the cable; don't repair it.
- Confirm it heats. FrostGuard's instructions say standing water in the pipe should feel warm within an hour.
- Check the insulation. Wet or missing insulation means the cable can't keep up.
How to quote it
Quote the system, not the cable. Measure the run, count the valves and spigots, and pick the cable length from the manufacturer's chart. Then list:
- Cable, sized to the pipe, plus thermostat if it's a separate part
- Removal of the old tape and insulation
- Insulation of the right type and thickness for that cable
- Application tape or ties, labels
- GFCI outlet or electrician, if the outlet isn't right
- Access: crawl space, skirting, pump house
- Insulation resistance test, with the reading on the invoice
- An optional yearly fall check
Price the labor from your hourly cost, not from what the cable costs at the store: see how to price plumbing jobs. If you don't own a megohmmeter yet, add it to your plumbing tools list before the cold sets in.
Plumbo, now on the App Store and Google Play, turns a voice note like "heat tape, 18 feet of crawl space line, needs a GFCI" into a quote from your own price book, then checks it for forgotten items before it goes out. Try the 60-second demo →
Frozen or burst pipe: what to tell the caller
When the call comes in, the homeowner needs a few steps before you arrive. From the Philadelphia Water Department and Moen:
- Check with a neighbor. If they have no water either, it may be a main break, not a frozen pipe.
- If a pipe has burst, shut off the water at the house-side valve near the meter. If the break is on the hot side, close the valve on top of the water heater too.
- Open the faucet on the frozen line so melting water can run out.
- Thaw it safely. A hair dryer, a space heater kept away from anything flammable, an electric heating pad, or towels soaked in hot water. Never a torch, a kerosene or propane heater, a charcoal stove or any open flame.
- Check the other faucets. If one pipe froze, others may have too.
- Call a plumber if they can't find the frozen spot, can't reach it, can't thaw it, or see a crack.
After the repair, offer the fix that stops the next call: insulation, sealing the draft, a reroute, or properly installed heat cable.
Sources
- Chemelex, Raychem FrostGuard 120 V Installation Instructions (PDF: GFCI, pipe types, insulation, fastening, valves, NEC articles, testing), checked October 9, 2026.
- Chemelex, Raychem FrostGuard data sheet (PDF, H59485: lengths, output, ground-fault protection), checked October 9, 2026.
- Easy Heat, Automatic Electric Water Pipe Heating Cable (AHB) Installation Instructions (PDF, 11001-118 Rev. 5: thermostat, overlap, insulation, plastic pipe, GFCI, maintenance), checked October 9, 2026.
- Easy Heat, HB Heating Cable Installation Instructions (PDF, 11001-001 Rev. 8: metal pipe only, thermostat control, GFCI, spacing), checked October 9, 2026.
- U.S. Consumer Product Safety Commission, CPSC Re-Issues Heat Tape Guidelines (January 22, 1996), checked October 9, 2026.
- Philadelphia Water Department, How to prevent frozen pipes (PDF: frozen and damaged pipe steps), checked October 9, 2026.
- Moen, How to Thaw Frozen Pipes, checked October 9, 2026.
- City of Minneapolis, Frozen water service lines (updated December 2, 2025), checked October 9, 2026.