A frozen pipe is a pipe where water has turned to ice and blocked the flow. The telltale sign is a faucet that runs a trickle or nothing at all in cold weather. The danger is not the ice itself. Ice expands, and pressure builds between the blockage and the closed faucet until the pipe can split.
If you catch it before it bursts, you can often thaw it safely. If a pipe has already split or water is spraying, shut off the main water valve and call our 24/7 line at (603) 815-9179 for burst pipe repair. The sections below cover what to do in the first few minutes.
Signs a pipe is frozen
- No water or only a trickle at one or more faucets in cold weather.
- Frost or a bulge on a visible pipe.
- Strange sounds, such as banging or gurgling, when you turn on a faucet.
- A smell from the drain, because the frozen pipe blocks the air flow.
- Only the hot or only the cold side is affected, which narrows the location.
Check the whole house. If water flows at some faucets and not others, the freeze is on a branch line. If nothing flows anywhere, the freeze may be at the main line, the meter or the well line.
What to do right away
- Open the faucetLeave it open so water can escape as the ice melts. Moving water also helps prevent a repeat freeze.
- Find the frozen sectionLook at pipes along exterior walls, in unheated crawlspaces, in garages and near the foundation, and run your hand along them. A section colder than the rest is likely frozen.
- Shut the main off if you see a splitA crack, a wet wall or a ceiling stain means the pipe has already failed. Close the main valve.
- Heat the pipe gentlyUse a hair dryer, a heating pad or warm towels. Start at the faucet end and work toward the blockage.
- Keep going until full flow returnsCheck other faucets too, since a second freeze can hide behind the first.
Never use an open flame
A propane torch, a kerosene heater or a portable stove can ignite wood framing or insulation and can overheat the pipe. Heated water can also scald you. A hair dryer is slower and much safer.
When to stop and call a plumber
Stop if you cannot find the frozen section, if the pipe is inside a wall or ceiling, or if you see a split. A thawed pipe can start leaking as soon as the ice melts, so keep the main valve handy and watch the area for a while after flow returns.
Call us if the freeze is on a service line, a well line or a meter, or if more than one area has no water. Our water service line repair crew handles buried lines, and our leak detection team can trace a hidden crack. We answer day and night, and we schedule same-day visits when the schedule allows.
Where pipes freeze first
| Location | Why it freezes | Prevention |
|---|---|---|
| Exterior wall behind a sink | Cold air reaches the pipe through the wall | Open the cabinet door and add insulation |
| Unheated crawlspace or garage | No heat source | Insulate pipes and seal drafts |
| Outdoor spigot and hose line | Water sits in the pipe | Drain, shut off the interior valve and cover the spigot |
| Basement near a window or sill | Air leaks around the sill | Seal gaps and insulate |
| Well line or pump house | Buried or outdoor piping | Check the depth and insulation, ask a plumber |
| Attic water line | Cold air and little heat | Insulate and keep the attic hatch closed |
How to keep pipes from freezing again
Prevention takes a little effort before the cold snap and saves a lot after. Most freezes happen in a narrow window when the temperature drops fast overnight.
Insulate
Foam pipe sleeves cost little and slow heat loss on exposed pipes.
Seal drafts
Fill gaps around pipes where they pass through walls or sills.
Let a faucet drip
A thin stream keeps water moving on the coldest night. It wastes a little water and can save a pipe.
Open cabinet doors
Let warm room air reach sink pipes on exterior walls.
Keep the heat on
If you travel, keep the thermostat at a safe temperature and have someone check the house.
Know your main valve
Everyone in the house should know where it is and how to close it.
What frozen pipe repair costs
A thaw or a repair after one is priced before we begin. The figure depends on:
- Whether the pipe merely froze or has split.
- How hard the pipe is to reach, such as inside a wall or under a slab.
- Pipe material and how much has to be replaced.
- Wall or ceiling repair needed after access.
- After-hours or holiday dispatch.
Homeowners insurance often covers sudden water damage from a burst pipe, though policies differ on frozen pipes in vacant homes. Read your policy and call your agent. For a real number, call (603) 815-9179.
Londonderry, NH note: wells, street lines and town help
Many Londonderry households are on private wells, so a freeze might be in the well line or pressure tank area. If water is gone at every faucet, check the pump and pressure tank and call a plumber before you restart anything. If you have questions about your water quality after a thaw, test your tap.
If you think the problem is on the street side of your shutoff, ask the Londonderry Department of Public Works at 603-432-1100, extension 460, whether the line is the town's or yours. In the 2026 construction season the town listed water main extensions on Old Nashua Road, Old Derry Road and South Road, so expect work and detours in those areas.
Pipes that burst from freezing are replaced with materials approved under the International Plumbing Code (IPC).
Questions we hear in Londonderry
A hair dryer can take half an hour or more for a short section. A long run or a pipe inside a wall may not thaw at all without professional help.
No, but the risk is real, especially when the freeze sits between the ice and a closed faucet. Keep a faucet open while thawing and watch for leaks after.
Yes. A thin stream on the coldest nights keeps water moving and can save a pipe. It uses a little water, which is cheaper than a repair.
Shut off the main water valve, switch off power to wet areas and call the 24/7 line at (603) 815-9179. We can dispatch a plumber the same day when the schedule allows.
Not always. If the pipe is dry and shows no cracks, you can monitor it and add insulation. If you see drips, stains or a bulge, call us.
Check the pump, the pressure tank and any exposed piping, and avoid restarting a frozen pump. Call a plumber, and after the thaw test your tap.
We thaw and repair pipes across Londonderry and in Derry and Hudson. For a pipe that froze inside a wall or under a floor, our leak detection service finds the crack before you open drywall.