Plumbing decision guide / 8 min read
Why do pipes burst in Texas, and what actually prevents it?
A hard freeze does not find your pipes at random. It finds the ones Texas builders put in the attic, in the exterior walls, and out at the hose bib, because none of that plumbing was ever meant to see real cold. What splits them is not what most homeowners think.
Short answer
Pipes burst here for two reasons. Texas builders run supply lines through unconditioned attics and exterior walls, and the failure itself does not work the way most people picture it. Ice does not pry the pipe open where it forms. It bridges the bore and makes a plug, and the water trapped between that plug and a closed faucet has nowhere to go as freezing continues. Pressure in that sealed column climbs until the pipe splits, often several feet from the ice. That is why opening a faucet at the end of a vulnerable run works, and why knowing where your main shutoff is does more to limit the damage than the size of the split ever will.
The split is usually not where the ice is
A pipe does not burst because ice pries it open at the frozen spot. Water does expand when it freezes, and the U.S. Geological Survey puts the density drop at about 9 percent, but that expansion has somewhere to go while the pipe is still open at one end. The break comes later. Ice grows inward from the pipe wall until it bridges the bore and forms a plug. Everything on the far side of that plug, between the ice and a closed faucet, is now a sealed column of water. Keep freezing the pipe and that column gets squeezed. Water does not compress, so pressure climbs until the pipe opens at its weakest point, often several feet from the ice, at a fitting inside a wall.
That one mechanism explains most of what follows. It is why opening a faucet works, and why the break is often nowhere near the coldest part of the run. It also explains why nothing leaks while the pipe is frozen. A split pipe packed with ice does not drip. It lets go at the thaw, usually the afternoon the weather breaks and everyone has left the house.
Texas plumbing sits on the cold side of the insulation
Northern construction keeps supply lines inside the heated envelope because it has to. Texas construction runs them through the attic and along exterior walls because that is faster and the attic is not expected to get cold. The Department of Energy’s Building America Solution Center puts it plainly in its plumbing guidance: in cold climates, avoid putting pipes in unconditioned attics. North Texas is not a cold climate by that classification, and that is the whole problem. The guidance that would have kept your lines warm was written for somewhere else, so it was never applied here.
A vented attic is outdoor air with a roof over it by design: the soffit and ridge vents exist to move outside air through it. And the insulation on the attic floor is there to protect your living space from the attic, not to protect your pipes, so a line draped over the joists sits on top of that blanket, on the cold side.
The weather here is not mild enough to make that safe. The National Weather Service office in Fort Worth puts the average first freeze at November 22 and the average last freeze at March 12, so the window runs about a third of the year. What swings is severity. The same office records 62 freeze days in the worst season on its list, 1977 to 1978, and 11 in the mildest, 2016 to 2017. A house can coast through several mild winters and then meet a season with five times as many freeze nights, which is why “it has been fine for years” says nothing about your plumbing.
NWS Fort Worth recorded a low of 2 degrees below zero at DFW on February 16, 2021, and 139 consecutive hours at or below freezing ending midday on February 19. The part that gets missed sits on the same page: that run only ties for fifth place on the office’s record list.
Where the breaks actually happen
| Where | Why it goes first | What to do about it |
|---|---|---|
| Supply lines in a vented attic | Attic air tracks outdoor air, and the lines sit above the insulation rather than under it | Insulate the runs, and learn which fixtures they feed |
| Hose bib with a hose still on it | A frost proof sillcock only works if the barrel drains when you shut it off, and a hose or closed nozzle holds that water in | Disconnect every hose in the fall, not the night before |
| Runs concealed in an exterior wall | Thin cavity with little insulation behind the pipe, and nothing visible from inside | Open cabinet doors under sinks on outside walls |
| The line feeding an attic or garage water heater | The cold inlet and flex connectors are exposed even though the tank holds heat | Insulate the inlet and outlet, and confirm the pan drain is clear |
| Above ground irrigation backflow assembly | A brass body full of standing water, fully exposed, on the house side of the meter | Shut off and drain the irrigation line, then wrap it |
The Texas Department of Insurance publishes homeowner guidance for this, and it tells you to start in the attic, where the department says many Texas homeowners saw pipes freeze. The rest of the list: wrap exposed pipes, wrap outdoor faucets, remove water hoses, and wrap pipes in unheated areas.
Insulation slows heat loss. It does not add heat, so foam sleeves buy time rather than immunity, and they will not carry an attic run through a long freeze with the power out. Where a run cannot be moved or warmed, the Building America Solution Center describes heat trace or tape: electric resistance cable applied to plumbing lines, drain lines, and vent stacks in cold climates to prevent freezing. And put the foam dome on the hose bib after the hose comes off, because a cover over a bib that still has a hose attached is insulating a barrel full of water.
What the drip actually does
The drip is not warming the pipe. A trickle of supply water carries almost no heat, and moving water freezes perfectly well. What the open faucet does is remove the closed end. With no sealed column between the ice and a shut valve, the pressure that would have split the pipe has an exit.
That changes how you use it.
- Open a fixture at the end of each vulnerable run, not just the one nearest the kitchen. A dripping tap on an interior wall does nothing for the attic line feeding the far bathroom.
- Open hot and cold. The Texas Department of Insurance says to let faucets drip from the cold and hot taps, and the hot side has its own exposed run back to the heater.
- A drip that stops on its own is information. A plug has formed upstream, and the protection you were counting on is gone.
- A drip is pressure relief, not a guarantee. A run that gets cold enough for long enough freezes solid with the tap open, and then you have no water even if nothing splits. For a severe, long freeze, draining the vulnerable runs and getting real heat into the space around them beats dripping.
Nobody volunteers the last one, because “leave a faucet dripping” is a shorter sentence.
Find your shutoff on a warm day
Plenty of homeowners have never located their main shutoff and go looking for the first time in the dark, with water coming through a ceiling. There are usually two valves. The one in the meter box near the curb belongs to the utility, normally needs a meter key, and sits under a lid that is often seized or packed with dirt. The one on your side is separate, commonly at the front hose bib, in the garage, or where the line enters the house. Find both this week.
Then turn yours off and back on. This is the step everybody skips, and it is the whole point. A valve that has not moved in decades can seize, or the packing can weep as soon as you break it loose. Finding that out on a Tuesday afternoon is a routine plumbing call. Finding it out during a burst is how minutes of water on the floor become hours of it. Buy a meter key, keep it somewhere you can find without a light, and show every adult in the house both valves, because the person home when it happens may not be you.
The moment you find water
- Shut the water off at your house valve. If it will not turn, go to the meter. The Texas Department of Insurance is direct about this: if your pipes freeze, turn off the water at the shutoff valve.
- Open a faucet at the lowest point in the house to drop pressure and let the lines drain.
- Kill power to anything near the water, and do not stand under a ceiling that is holding it.
- Shut down the water heater. An electric unit will destroy its elements if it comes on with the tank drained down.
- Photograph everything before you move it, then call your insurer and a licensed plumber.
- Start moving air. Drying is the one part still under your control.
How long it ran decides the damage
A crack the width of a pencil lead in a pressurized supply line moves water continuously and quietly. The size of the opening barely matters. What decides the damage is how long it ran before somebody closed a valve, and whether it ran above a ceiling or onto a garage floor. Drywall, insulation, flooring, cabinets, and drying all scale with duration, and together they add up to far more work than the pipe repair itself.
One insurance note is worth having in advance. The Texas Department of Insurance states that home and renters policies might not pay for damages caused by frozen pipes if you did not take steps to protect your pipes, such as keeping the heater on in your house. Ask your own carrier what it expects of you, because that answer lives in your contract rather than in a general rule about Texas.
Who you let in afterward
Plumbing here is licensed by the Texas State Board of Plumbing Examiners. Its consumer guidance tells you to get the Responsible Master Plumber’s license number for the company, and that number should appear in all of the company’s advertisements. The board’s license search then confirms both that the license is valid and that a Certificate of Insurance is on file, which is the part hardly anyone thinks to check. The board also says to ask your city’s plumbing inspection department whether the work needs a permit and inspection, since permits are a city matter rather than a state one.
If the freeze took your water heater or the lines feeding it, should you repair or replace your water heater covers that decision. If you are choosing between contractors, how to choose a contractor in Dallas-Fort Worth covers what to compare.
This guide gives no threshold temperature for when a pipe starts to freeze. The number in wide circulation traces back to research we could not read for ourselves, so we left it out.
Sources
- National Weather Service, Fort Worth, February 2021 Historic Winter Storm and Arctic Outbreak.
- National Weather Service, Fort Worth, DFW Freeze Summary.
- U.S. Geological Survey Water Science School, Water Density.
- Building America Solution Center, U.S. Department of Energy, Insulating Plumbing Pipes.
- Texas Department of Insurance, Winter storms: Tips for preparing your house and pipes.
- Texas Department of Insurance, Avoid frozen pipes and water damage by taking steps now.
- Texas State Board of Plumbing Examiners, Consumer Information.
Sources
- February 2021: Historic Winter Storm and Arctic Outbreak National Weather Service, Fort Worth
- DFW Freeze Summary National Weather Service, Fort Worth
- Water Density (Water Science School) U.S. Geological Survey
- Insulating Plumbing Pipes Building America Solution Center, U.S. Department of Energy
- Winter storms: Tips for preparing your house and pipes Texas Department of Insurance
- Avoid frozen pipes and water damage by taking steps now Texas Department of Insurance
- Consumer Information Texas State Board of Plumbing Examiners
Common questions
Why do pipes burst in Texas when the same pipes do not burst up north?
The pipe is in a different place. Northern construction keeps supply lines inside the heated envelope because it has to, while Texas construction runs them through vented attics and along exterior walls, which is faster and works fine right up until a hard freeze. The Department of Energy's Building America Solution Center guidance on plumbing says to avoid putting pipes in unconditioned attics in cold climates, and North Texas is not a cold climate by that classification, so the guidance was never aimed here. The second half of the problem gets even less attention: the insulation on your attic floor is there to protect the rooms below it, so a water line lying on top of the joists sits on the cold side of that blanket. A vented attic is outdoor air with a roof over it by design, since the soffit and ridge vents are there to move outside air through it. That is why freeze failures cluster in attics, exterior walls, and hose bibs rather than in the middle of the house. It is also why a house that came through several winters untouched proves nothing about the next one.
Does a frozen pipe actually burst at the ice?
Usually not, and this is the part people tend to have backwards. Water does expand when it freezes, about 9 percent by the U.S. Geological Survey's figure for the density change, but that expansion has somewhere to go while the pipe is still open at one end. The damage comes from what happens after ice bridges the pipe and forms a plug. The water trapped between that plug and a closed faucet is now a sealed column, and continued freezing squeezes it against a valve that will not open. Water does not compress, so pressure climbs until the pipe fails at its weakest point, which is often several feet from the ice and frequently at a fitting inside a wall. A plumber chasing a freeze break therefore does not simply look where the pipe was coldest, and the run you thought you had protected can still split if the fixture at the end of it was shut.
Does letting a faucet drip actually prevent frozen pipes?
It prevents the burst, not the freeze, and that difference changes how you should use it. An open faucet does not warm the pipe, because a trickle of supply water carries almost no heat and moving water freezes perfectly well. What the open tap does is remove the closed end, so ice can form without sealing a pressurized column against a shut valve, and the pressure that would have split the pipe has somewhere to go. So drip the fixture at the far end of each vulnerable run rather than whichever tap is convenient, because a drip in the kitchen does nothing for the attic line feeding a back bathroom. The Texas Department of Insurance advises dripping the cold and hot taps, and the hot side has its own exposed run. And if a drip stops on its own during a freeze, that is not the cold slowing it down. A plug has already formed upstream, and the protection you were counting on is gone.
Where is my main water shutoff valve, and what if it will not turn?
There are usually two, and plenty of homeowners have located neither. One sits in the meter box near the curb, belongs to the water utility, normally needs a meter key, and hides under a lid that is often seized or packed with dirt. The other is on your side of the meter, commonly at the front hose bib, in the garage, or where the service line enters the house. Find both on a dry afternoon rather than during an emergency, then actually turn yours off and back on, because a valve that has not moved in decades can seize and the stem packing sometimes weeps once you break it loose. Finding that out on an ordinary Tuesday is a routine plumbing call. Finding it out with water coming through a ceiling is how minutes of water on the floor become hours of it. Buy a meter key, keep it somewhere you can find without a flashlight, and show every adult in the house both valves, because the person home when it happens may not be you.
My pipes are frozen but nothing has burst yet. What should I do?
Open the faucet on that run first, both hot and cold, so any further ice is not sealing a pressurized column against a closed valve. Then get heat to the space rather than to the pipe: open cabinet doors under sinks on exterior walls, and warm a garage or attic if you can do it safely. Never put an open flame on a pipe. A pipe that has already split will not leak while it is still frozen, because the ice is its own plug, so a dry floor right now is not evidence the pipe is intact. The leak starts at the thaw. The Texas Department of Insurance is direct about this case: if your pipes freeze, turn off the water at the shutoff valve, which prevents broken pipes from leaking into your house after they thaw. If you are going to be away when the weather breaks, shut it off before you go.
Do I still need to worry about outdoor faucets if I have frost proof hose bibs?
Yes, because a frost proof sillcock is only frost proof if it can drain. Its shutoff sits back inside the warm wall, and when you close it the water left in the barrel is supposed to run out the spout. Leave a hose, a splitter, or a closed nozzle attached and that water cannot leave. It freezes inside the barrel, which is inside your wall, and the split happens where you cannot see it. The timing is the nasty part. Nothing leaks in January, because the valve upstream of the split is closed. You find out in April, when you open the bib for the first time and water pours into the wall cavity instead of out the spout. Removing water hoses is on the Texas Department of Insurance's winter list. Do it in the fall, not on the night the forecast turns.
Will homeowners insurance pay for a burst pipe in Texas?
Ask your own carrier, because this is settled by your policy rather than by a general rule about the state. The Texas Department of Insurance does state that home and renters policies might not pay for damages caused by frozen pipes if you did not take steps to protect your pipes, such as keeping the heater on in your house. That makes your prevention record part of the claim, which is an argument for keeping it simple and documented: hoses off, wraps on, heat left running when you travel. If a burst does happen, photograph everything before you start pulling carpet or cutting drywall, because the drying crew will erase the evidence of what the water actually did. And keep the proportions in mind. The plumbing repair is usually the small part, while drywall, insulation, flooring, cabinets, and drying make up the bulk of the work, and all of that scales with how long the water ran before somebody found the valve.
If you would rather just talk to someone
Lantern is a family-owned team covering HVAC, plumbing, electrical, and project work across Dallas-Fort Worth. No obligation, and we would rather tell you a system has years left than sell you one it does not need.
Talk to a licensed pro, not a call center.
One team for HVAC, plumbing, electrical, and project work across Dallas-Fort Worth.
Book a visit