Frozen pipes in a New Jersey house: what to do tonight, which pipes freeze and why, and the fixes that end it

At what temperature do pipes freeze in a New Jersey house?

Water freezes at 32°F. Your living room never gets there. The real question is how cold the air around the pipe gets. A pipe in an exterior wall, a crawlspace or a garage ceiling is separated from the outdoors by sheathing and siding, not by the furnace. On a 10°F night with wind, that cavity can sit below freezing for hours while the thermostat reads 68.

The model residential code builders work from, the IRC, draws the line at a winter design temperature of 32°F or lower. In those places a water pipe may not go outside the building, in an exterior wall, in an attic or in a crawlspace “unless adequate provision is made to protect it from freezing by insulation or heat or both” (IRC 2021, P2603.5). The same section puts the water service pipe at least 12 inches deep and 6 inches below the frost line. New Jersey is on the cold side of that line every winter. Older houses were built long before the rule.

How cold Newark gets, from the 30-year record

NOAA's 1991–2020 climate normals for Newark Liberty International Airport, a long-record station near Belleville, Bloomfield and Nutley (station USW00014734):

Read the January line twice. A night at or below 20°F is close to certain, and 9 winters in 10 bring a night at or below 16°F. December is the trap. The normal low is barely below freezing, so nobody has done the fall list yet, and 4 Decembers in 5 still deliver a 20°F night. The first hard freeze is the first test the house gets that winter.

Which pipes freeze in a New Jersey house, and why

The Red Cross lists the usual suspects: hose bibs, supply lines in unheated basements, crawlspaces, attics, garages and kitchen cabinets, and pipes against exterior walls with little or no insulation. Here is what that list looks like in an Essex County house, room by room.

• The kitchen sink on an outside wall. The supply lines come up inside the exterior wall behind the cabinet, often with nothing behind them, and the closed doors keep room heat out. The IRC now says keep pipes out of exterior walls. In 1925 nobody did.
• The bathroom over the garage. The supply lines run through the floor joists above an unheated garage. If the garage ceiling was never insulated, or the batts were stuffed below the pipes instead of behind them, the pipes sit in garage air. One open door on a 10°F night does the rest.
• The crawlspace. Vented crawlspaces under additions and older kitchens run outdoor air straight past the plumbing. Building America's cold-climate guide says to seal every penetration through the rim joist and walls with closed-cell foam, insulate the runs, and consider heat trace.
• The porch that became a room. A sunroom or enclosed porch on piers, with a floor a few inches above outdoor air. When a sink or a powder room gets added, the lines run in a floor nobody insulated. We build these conversions, and the floor is where the work is.
• The finished basement with a drop ceiling. The pipes above the tiles run along the rim joist, the band of wood sitting on top of the foundation wall. Building America lists the rim joist among the places to seal and insulate. A finished ceiling hides the cold, and hides the leak until the tiles sag.
• The addition with a bare rim joist. Even a well-built addition can leave the rim joist uninsulated where the new floor meets the old house. The gap behind the baseboard is where the cold comes in, and where the pipe to the new bathroom runs.
• The garage laundry or slop sink. Any water line in an unheated garage is outdoor plumbing in January. Keep the door shut, sleeve the pipe, and plan to move the line when the garage gets finished.
• Outside hose bibs. IBHS notes that homes built before 2010 typically do not have frost-proof outdoor faucets. The old style holds water right at the outside wall. Drain it every fall, or have the plumber swap it for a frost-free sillcock.
• The water meter and service entry. The Red Cross names the spot where the service comes through the foundation as a likely freeze. The meter is usually right there, in the coldest corner of the basement, against a wall that was never insulated.

How much to drip, and from which faucet

Nobody authoritative publishes a drips-per-minute number, and we will not invent one. The Red Cross says running water through the pipe, “even at a trickle,” helps prevent freezing. It says to let the cold water drip from the faucet served by the exposed pipe. IBHS says to let all faucets drip during extreme cold.

Our reading of both: a thin, steady trickle, not an occasional drop, from every faucet whose supply runs through a cold wall, a crawlspace or a garage ceiling. On a single-handle faucet, set the handle to the middle so both lines move. The Red Cross notes both hot and cold can freeze in the same cold space. A week of this costs less than a drywall ceiling.

Without heat, or without power

A furnace that quits on the coldest night, or a storm that takes the power, turns the whole house into the garage. The order changes:

• Open every faucet to a trickle and every cabinet door. The Red Cross tips for exposed pipes now apply to all of them, because the room is the cold space.
• If the outage will outlast the night, shut the main and drain. IBHS gives this step for a house left empty for more than a week in subfreezing weather, and it is the same move when the heat is out: close the main valve slowly, then open faucets on the lowest floor and let the lines drain. Empty pipes cannot burst.
• Heat the plumbing wall, not the house. With a generator, keep the kitchen and the room where the main comes in above freezing. A space heater stays in the open, away from anything that burns, never in a cabinet.
• Never bring a propane or kerosene heater, a charcoal grill or any open flame inside. The Red Cross bans every one of them for thawing. The carbon monoxide risk is worse than the burst.

Thawing a frozen pipe safely

The sign is a faucet that gives a trickle or nothing while the rest of the house works. The Red Cross's method, in order:

1. 1Find the frozen section. Follow the line from the dead faucet toward the main. Likely places are the exterior wall behind the fixture and where the service enters through the foundation. Frost or a bulge on an exposed pipe gives it away.
2. 2Open the faucet and leave it open. As the ice melts, water has to move. An open faucet relieves the pressure between the ice plug and the valve, which is where pipes split.
3. 3Warm the pipe gently. An electric heating pad wrapped around the pipe, a hair dryer, towels soaked in hot water, or a space heater kept away from anything flammable.
4. 4Never use a flame. No blowtorch, no propane or kerosene heater, no charcoal stove, no open flame of any kind. That is the Red Cross's exact list. A torch on a soldered joint starts a fire inside the wall.
5. 5Keep going until full pressure is back, then check every other faucet. If one pipe froze, others may have. The Red Cross says to check them all.
6. 6Cannot find it, reach it or thaw it? Shut the main and call a plumber. If the frozen section is inside a finished wall or ceiling, the plumber may need an opening. That opening is where our work starts, and it is a small patch if it is cut cleanly.

The fixes that end it

Dripping faucets every January is a workaround. The U.S. Department of Energy's Building America Solution Center spells out the permanent version. Most of it is carpentry and insulation, not plumbing. From cheapest to most involved:

• Pipe sleeves on every exposed run. Foam tube insulation on hot and cold lines in the basement, crawlspace and garage. Building America's detail: tape the seams, secure the sleeve every 1 to 2 feet, and seal the holes where pipes pass through framing with caulk or foam. A sleeve slows the cold. It does not stop it, so it is the first layer, not the only one.
• Air seal the cavity the pipe lives in. Moving cold air freezes a pipe faster than still cold air. Building America's instruction for pipes in an exterior wall: caulk or foam every seam between the back of the cavity and the framing, and seal every hole drilled for the piping.
• Insulate behind the pipe, not in front of it. The insulation goes between the pipe and the outdoors, with the pipe on the warm side. Batts get split lengthwise, half behind the pipe and half in front. Insulation stuffed in front of a pipe makes it colder.
• Seal and insulate the rim joist. The band of wood on top of the foundation wall is where basement pipes freeze. Building America says to seal every penetration through it with closed-cell foam; its method is rigid foam cut to fit each joist bay with the edges sealed, or spray foam across the band, done before a basement ceiling closes it in.
• Frost-free hose bibs, pitched to drain. A frost-free sillcock puts the valve seat well inside the warm wall, so there is no water at the cold end. Building America says to slope the pipe to it slightly downward. The plumber installs it. We open and close the wall around it if the siding or trim has to move.
• Move the run off the exterior wall during a remodel. The permanent fix for the kitchen sink on an outside wall. Building America's first rule is to keep pipes out of exterior walls and line fixtures up with interior walls. A kitchen remodel or bathroom remodel is the one time the wall is open and the plumber is on site. Moving the lines then takes hours instead of a demolition.
• Insulate the floor of a porch conversion and the ceiling of a garage. Any room with outdoor air under it gets a sealed, insulated floor before the plumbing goes in. On an addition or porch conversion this is part of the framing, not an extra.
• Heat cable, as a stopgap with limits. Building America allows thermostat-controlled heat tape on piping in unconditioned basements, crawlspaces, attics and exterior walls, plugged only into a GFCI outlet and installed where it can be reached and replaced. It warns that badly installed heat trace can be a fire hazard. It keeps one pipe alive through one winter. It does not fix the wall, and it fails when the power does.
• PEX where the plumber re-pipes. Building America notes that cross-linked polyethylene has proven more robust to freeze-thaw cycling than copper. It still freezes; it forgives more. Worth asking the plumber about when a line gets replaced after a burst.

The building side of this list is our trades and repairs work. In a basement it is the first step of finishing the basement.

After a burst: the first hour, the first two days, and the rebuild

The Insurance Information Institute counts about 1 in 60 homes with a homeowners policy filing a property damage claim for water damage or freezing each year (III). Here is the sequence that keeps a burst pipe a plumbing bill instead of a gut renovation.

The first hour

• Shut the main water valve. IBHS puts this first. If water reached the electrical panel or outlets, leave the power to that area off until an electrician looks.
• Open faucets to drain the pressure, then call a plumber for the pipe. IBHS: call a plumber to make repairs for any burst pipes.
• Photograph and video everything before you touch it. The III's claim guidance: document the damage, then protect the property from more damage, and keep damaged items for the adjuster if you can.
• Call the insurer and start the claim. Save every receipt, including for fans, a dehumidifier or a hotel night. The III notes most policies cover additional living expenses with proof of cost.

The first 24 to 48 hours

This is the mold clock. The EPA says water-damaged areas and items must be dried within 24 to 48 hours to prevent mold growth, and that when they are, “in most cases mold will not grow” (EPA). The CDC gives the same window for drying out a home after a flood (CDC). On the job that means:

• Get the water out and the air moving within hours: pump, wet vacuum, fans and a dehumidifier. A restoration company does this at scale. For one room, a contractor or a determined homeowner can.
• Open what is wet. Water inside a wall or ceiling does not dry through paint. Wet drywall gets cut out above the water line. The EPA lists the back of drywall, the top of ceiling tiles and the underside of carpet pads as places mold hides.
• Porous materials that soaked are usually gone. The EPA says ceiling tiles, carpet and other absorbent materials may have to be thrown away once mold takes hold. Wet batt insulation, carpet pad and particleboard cabinet bottoms fall in that group.
• Hard surfaces get cleaned and dried. Framing, subfloor and tile can usually be saved if they dry inside the window.

The rebuild, in order

1. 1The plumber repairs or replaces the pipe. If the run is in an exterior wall, this is the moment to move it, or at least insulate behind it before the wall closes.
2. 2Everything dries and gets checked with a moisture meter before any new material goes on. Closing a damp wall restarts the mold clock behind the paint.
3. 3Insulation and air sealing go back better than they came out. The cavity that froze gets sealed, insulated behind the pipe, and the rim joist foamed.
4. 4Drywall, tape and paint. Ceilings first, then walls. A clean cutout along a joist line makes the patch invisible.
5. 5Flooring. Laminate and engineered floors that swelled are replaced. Solid hardwood sometimes dries flat and sands out.
6. 6Cabinets, vanities and trim last. Particleboard boxes that sat in water do not come back. A kitchen that floods from the sink wall usually loses the sink base and its neighbors. The rest can often stay.

Who does what: the plumber owns the pipe, the restoration company owns the drying when the damage is large, and the general contractor owns everything that gets rebuilt. On a kitchen or bathroom that flooded, that rebuild is a kitchen or bathroom job with the demolition already done. Our drywall and flooring prices are on the trades and repairs page.

The New Jersey permit note

New Jersey's construction code lists what needs no permit at all. Under N.J.A.C. 5:23-2.7, ordinary maintenance includes “the installation of insulation, except foam plastic insulation, when installed adjacent to or not more than one and a half inches from an interior finish.” Replacing a hose bib valve is on the same list, as long as the new one has an approved vacuum breaker. So sleeving pipes and batt-insulating an open basement wall need no permit, inspection or notice. Spray foam against a wall that will be finished over is the exception, and it gets a permit.

Replacing existing water piping with new material of like capacity is “minor work” under N.J.A.C. 5:23-2.17A in the same document. Minor work takes a permit, but the work may start once the town has been notified, with the application filed within five business days. The plumber files that one. Drywall over less than 25 percent of the wall area in a one- or two-family house is ordinary maintenance too, which covers most burst-pipe patches. A full ceiling or a gutted kitchen is a permit, and we file it.