Heat tape on a water pipe (C) Daniel Friedman Where & How to Add Heat or Insulation to Prevent Frozen Pipes

  • HEAT TAPES to AVOID FROZEN PIPES - CONTENTS: use of heat tapes on water supply piping, drain piping, or PVC plastic supply or drain piping. Pipe Heat Tape Safety Guide. GFCI outlets for heat tapes? How the presence of heat tapes and plumbing repairs may give clues to a building's history of problems with freezing pipes.
  • POST a QUESTION or READ FAQs about how to protect buildings from freeze damage: prevent frozen pipes, frost heaves, cracking due to freezing, and prevent water and mold damage that follows frozen, burst pipes.

Freeze-protection for buildings: This article explains where, why, and how to add heat at cold problem spots to avoid freezing pipes. We discuss the safe use of heat tapes in buildings and warn about unsafe heating tapes and fire hazards.

The articles at this website will answer most questions about freeze protection for piping and other building plumbing and heating system components: how to winterize a building to avoid frozen pipes, and how to thaw frozen water supply & drain piping, wells, & water tanks. We discuss various methods to give each spot in danger of freezing its own heat source.

For example simple passive heating may be sufficient to avoid freezing in some locations: in kitchens and bathrooms we may leave open vanity cabinet doors to permit warmer building air to reach pipes in those areas. Our page top photo shows both a plumbing repair (charred joist, sloppy soldering) and a yellow heat tape in use. What can we infer about the building's frozen pipe history from this photo? Answers are in the article below.

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Guide to Using Heat Tapes to Protect Pipes From Freezing

Heat tape on a water pipe (C) Daniel FriedmanUsing heat tapes to protect pipes from freezing: heat tapes are one of the simplest and more commonly used methods of protecting sections of water pipes from freezing.

The photograph of the yellow heat tape at left contains some helpful information:

  1. The presence of a heat tape indoors indicates that someone has already had reason to be concerned about freezing pipes in this area of the building.
  2. The insulation, in the right edge of the photo, if it is wrapped around the pipe to cover the heating tape, can create a fire hazard by causing the heat tape to overheat when it is in use.
  3. The charred joist behind the copper piping in this photo has nothing to do with the heat tape itself, was not caused by the heat tape, and was almost certainly caused during soldering of the pipe tee to the three copper lines - the plumber didn't bother to place a heat shield behind the piping to protect the wood. However it's possible that this solder job indicates previous repairs on frozen pipes in this area.

Avoid a fire hazard with heating tapes: But if the heat tape is not correctly installed it can be a fire hazard (as well as unreliable). Heat tape safety suggestions from the US CPSC are offered below.

Heating tapes work fine on copper, brass, or galvanized iron piping, for both supply and drain piping but we prefer the type that use an automatic thermostat so that we are not using electricity unnecessarily. Be sure that the heat tape is properly installed and that you don't cover the thermostat nor place it in a warm rather than cold spot on the piping.

How to Install Heating Tapes on Plastic or PVC Supply or Drain Piping

If your building plumbing pipes are plastic, such as PVC water piping, use only pipe heat tape that has an automatic thermostat to control the heat tape temperature. Otherwise a very hot heating tape may damage the piping or even cause a leak.

Watch out: some heating tapes cannot safely be used on drain pipes, particularly PVC piping, possibly because of a concern for heat damage to the piping. Be sure to check with the manufacturer about the intended application of their heating tape. The tape installation specs for PVC or other plastic piping may specify the spacing used when spiraling the heat tape around the pipe to avoid any risk of overheating.

Be sure to read PIPE HEAT TAPE SAFETY GUIDE from the US CPSC (below in this same article)

Several manufacturers provide pipe heating cables that can be used on all types of piping materials including plastic or PVC, but be sure to read the instructions. Depending on the pipe material, different heat tape installation procedures are recommended. Here are some examples provided by Easy Heat®.

The company also provides an electrical receptacle adapter that provides thermostatic control to turn the heating cable on and off as needed. [9] Other heating cables that can work in these applications are available from RayChem® [11] and other manufacturers.

Temperature-controlled cable runs straight along pipe and valves, held in place by application tape and plugs into grounded electrical outlet. Keeps water flowing down to -380. For odd lengths of pipe over 3/4 inches in diameter, we recommend two separate cables on opposite sides of the pipe with up to 3 feet of overrun at center of pipe run.

Metal pipe requires 1/2-inch fiberglass insulation around cable.

For plastic pipe, its recommended wrapping pipe with aluminum foil before cable installation.

The traditional resistance cable produces a fixed amount of heat based on the electrical line feed. It comes with a built-in thermostat that switches the flow of electricity on and off based on temperature. 120 volts. 7 watts per foot. Not U.L. Listed. [9]

How to Protect a Sump Pump from Freezing

Sump pump and drain piping freeze protection: for indoor sump pumps and drains follow our advice above regarding metal vs. plastic piping and heat tape selection. If your sump pump drain line is exposed to severe cold above ground outdoors it may be difficult to keep it from freezing.

A common water entry problem we've seen is during spring thaw in northern climates. The ground surface may be frozen but melting snow sends water into building around and through foundation walls, especially if you've shoveled snow piled up against the foundation walls.

If the building is relying on a sump pump to remove foundation water then this is just the time we don't want our sump pump drain to freeze. If the drain can't be buried below the frost line all the way from the building to its final destination, we've had some success using heat cables intended for outdoor and wet conditions, even placing the tape inside the pipe in some installations.

Follow the heating tape manufacturer's instructions and be sure to provide a means of easy tape replacement when needed - you don't want to have to dig up the entire line over again just to replace a heating tape on a sump pump drain.

Heating tape safety and proper installation are discussed just below.

Other Common Locations for Heating Cables or Tapes to Prevent Pipe Freeze Damage

Common locations where heating tapes are used on plumbing to prevent freezing pipes include:

  • Water pipes run through attics
  • Water pipes run through un-heated crawl spaces
  • Water pipes and equipment in un-heated garages
  • Water equipment in well pits
  • Water pipes running under porches
  • Heating oil piping where heating oil is stored in outdoor above ground oil storage tanks. -

Some older or less costly models of heating tapes present a fire risk, particularly if the heating tape is crossed over itself. Be sure to read the product specifications, safety warnings, and installation guide before installing a heating tape on building piping of any kind.

Pipe Heat Tape Safety Guide from the US CPSC

Pipe heating tape thermostat (C) Daniel Friedman

The U.S. CPSC has provided safety recommendations for homeowners using heat tapes to help prevent fires:

  • Replace heat tapes that are older than three years
  • Use only heat tapes certified to meet recognized voluntary fire safety standards such as those provided by Underwriters Laboratories (UL), the Canadian Standards Association (CSA), and the Factory Mutual Research Corporation (FMRC).
  • Plug the grounded (3-prong) plug into a grounded GFCI (ground-fault circuit interrupter) protected electrical outlet
  • Don't cross the heat tape across itself unless the manufacturer says that's acceptable - crossed heat tapes can overheat and start a fire
  • Put the heating tape on the surface of the pipe to be protected from freezing, not on top of pipe insulation, and do not cover the heating tape with insulation unless the manufacturer says that's acceptable. Use only non-combustible insulation on pipes where heating tapes are installed (like fiberglass insulation). Foam or vinyl pipe insulation may catch on fire from a faulty heat tape or faulty heat tape installation.
  • Protect the sealed end-cap of the heat tape (see our photo above) from damage and water leaks which could cause a short circuit or fire.
  • Use heating tape only for the application approved for that particular heating tape, such as for use on piping. Some heat tapes are designed for use in gutters or driveways while others are designed for use on piping or fuel piping.
  • Be sure that the heat tape thermostat (if one is provided) is placed where the instructions say. For example some heat tape thermostats should be placed in contact with the pipe, others left hanging in air. (See our photo above)
  • Replace any heat tape that is discolored (a sign of overheating), cracked, melted, or damaged in any way.

Advice For & Warnings About Using GFCI-protected Circuits to Power Heat Tapes to Avoid Fires

Watch out: some models of heat tapes used for freeze protection can cause a building fire if the tapes are not installed according to the manufacturer's recommendations, particularly if the tape crosses over itself.

As Ryan Duffy points out, connecting the heat tape to a GFCI-protected circuit can substantially reduce the risk of heat tape fires. However if the GFCI-protected heat tape circuit trips-off during typical current leakage conditions and without drawing attention of the building occupants, the risk of freeze damaged piping, leaks, water damage, and mold damage will be increased.

The US CPSC recommended in 1994 that HUD consider dropping its no-GFCI-on-Heat-Tape-Circuit provision, and that heat tape powering electrical circuits be be protected with a GFCI device in the electrical panel rather than at the electrical receptacle or "outlet". Ground fault protection was first required in the 1987 NEC for heat tapes that did not have a metal covering.

In 1996/1999 the NEC expanded the requirements for GFCI protection and specified that mobile homes would have at least one heat tape receptacle. [A significant number of heat tape-related fires occurred in mobile and manufactured homes.]


Guide to Pipe Insulation to Prevent Freezing

Foam pipe insulation (C) Daniel FriedmanAdd Water Pipe insulation to prevent freezing: can be added to protect pipes routed through un-heated areas or near cold building corners. We particularly like to add slip-on foam pipe insulation where a plumbing line is run past a cold spot that is hard to warm up.

Some writers believe that if you insulate all of your water supply piping you won't have a frozen pipe problem. That may be a bit optimistic: we fear that a cold corner somewhere will be missed and left un insulated, or that a house left without heat for too long will get cold enough to freeze even an insulated pipe.

The advantage of insulating pipes is that it slows the rate at which a water pipe will freeze, possibly getting the pipe through the coldest part of the night and into a (hopefully) warmer daytime to warm-up again.

Remember, when insulating a water pipe, that you need to insulate all of it. Don't leave those awkward elbows or pipe tees un insulated.

Here is a speculative warning about relying on pipe insulation alone to avoid freezing, that is, we don't have hard science to back up this view: Insulation on a water pipe will protect the pipe from freezing during a brief very cold spell. But during a period of prolonged very cold nights and only moderately warmer days, we wonder if the insulation permits the pipes to accumulate "cold" rather than warmth, ultimately reaching the freezing point.

Plastic piping to resist freezing: modern plastic piping is considerably more tolerant of freezing without bursting than copper or steel water pipes. In a home intended for regular winterization some builders use exclusively plastic pipes to resist freeze damage. Be careful: even when freeze-tolerant piping is used, the piping connections, elbows, unions, couplings, and plumbing fixtures are still at risk of frost damage.

Watch out: even when freeze-tolerant piping is used, the piping connections, elbows, unions, couplings, and plumbing fixtures are still at risk of frost damage.

Reader Question: doesn't the use of "self-regulated" heat tape mean I can safely add lots of pipe insulation too?

(Nov 11, 2014) Jera Anderson said:

I've installed two EasyHeat brand heat tapes per the instructions on my PEX lines which are installed in an unheated crawlspace beneath the house. I pre-wrapped all the PEX with aluminum foil, then secured the tape to the pipe with 3" wide aluminum tape. Installation instructions suggested securing with high temp electrical tape or an equivalent.

The manufacturer's documentation warns to use no more than 1/2" non-combustable insulation (fiberglass) wrapped around the installation, then a vapor barrier (plastic wrap) to keep the insulation dry.

My question is this: 1/2" fiberglass seems inadequate to me and wouldn't hold very much heat near the pipe. The warnings are the heat tape can overheat and cause a fire hazard if more than 1/2" is used. Can this type of self-regulated tape (it has its own thermostat and turns off when water temp reaches 40-50 degrees F.) actually generate enough heat to set PEX on fire if more than 1/2" fiberglass is used? Thanks!

Reply: no.


At the end of the day we are wise to follow the manufacturer's instructions - they have a lot at stake in the successful and safe use of their product. A hazard of improper use of heating tapes is a building fire. While the heat tape may be described as self-regulating, the manufacturer has decided, probably based on testing and UL listing procedures, just what level if insulation is safe with their product.

Therefore if we are in doubt about the adequacy of a single step aimed at avoiding frozen pipes I'd prefer to take other proper steps such as those described in this article series: finding and fixing drafts, or adding area heat for example. Often we find that even a small amount of heat added in an area, sometimes just an incandescent light bulb, is enough to avoid a freezing problem.

At INSULATION to AVOID FROZEN PIPES we explain that pipe insulation does not always work as expected as a freeze-proofing measure: depending on how ambient temperatures cycle the insulation can also prevent piping from gaining heat during warmer intervals, sometimes actually increasing freeze risk during long cold periods with brief warming intervals.


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