Frozen or Burst Pipe? How to Tell the Difference

Telling a frozen or burst pipe apart comes down to one question: is water missing, or is water escaping?

A pipe full of ice blocks the flow, so a faucet sputters and quits while the rest of the house works normally.

A pipe that has split lets water out, so pressure sags across fixtures and water shows up somewhere it should not.

The trap is that both can be true at once. Pipes usually freeze around 20 degrees Fahrenheit rather than 32, and the same ice that split the pipe can keep it sealed for hours.

Signs the pipe is frozen but still intact

Work through these before touching anything with heat:

• No water, or a thin trickle, from one fixture while others run fine.
• Frost or condensation on an exposed pipe run in a basement, crawl space, or garage.
• A visible bulge in a copper or plastic line where ice has expanded inside it.
• Gurgling, whistling, or banging when you open the tap and air moves past the ice.
• Sewer smells at a drain, which can mean a drain line is iced and gas is backing up.

The one fixture clue is the strongest one. Freezing happens at the coldest section of a run, so it knocks out a single line, not the whole house.

Touch the pipe if you can reach it. A frozen section feels colder than the pipe on either side of it, and often sweats.

Nothing wet anywhere plus no water at the tap is the classic frozen but intact picture.

Signs the pipe has already burst

A burst announces itself through pressure and moisture, not through silence.

• Pressure drops at several fixtures at once, then keeps falling.
• Water appears on a ceiling, down a wall, at the base of a wall, or across a basement floor.
• A stain or bubble in drywall that grows while you watch it.
• Running water you can hear inside a wall with every tap closed.
• A warm or damp patch on the floor above a slab line.

One more that people miss: a sudden spike in the water bill after a cold snap, with no other explanation.

A burst on a hot line has an extra tell. The water heater runs constantly because it keeps reheating water that never reaches a tap.

Pressure that drops house wide is the important distinction. One dead fixture is ice, falling pressure everywhere is an open pipe.

If your basement is already taking water, stop reading and start with the first steps after a burst pipe.

The water meter test that settles it

This is the check that turns a guess into an answer, and it takes about ten minutes.

Turn off every fixture and appliance that uses water: taps, toilets, dishwasher, washer, ice maker, and any humidifier.

Find the water meter, usually near the main shutoff or at the street, and note the reading and the position of the small leak indicator dial.

Wait fifteen minutes without using any water, then read it again.

Movement means water is leaving the system, which means a split somewhere. No movement points to ice with the pipe still whole.

Before you go further, know exactly where your main shutoff is and how to close it, because the next step can release water fast.

Why a burst pipe hides until it thaws

Here is the part most guides skip, and it is the reason people get surprised by a flood.

Freezing water expands and splits the pipe, but the ice plug stays in place and seals the opening it just made.

So the meter can sit perfectly still while a six inch split waits inside the wall for the temperature to come up.

That is why the damage so often arrives during the thaw, sometimes a day or two after the cold snap ends.

Treat every frozen pipe as a possible burst. Be present when it thaws, with the main shutoff located and clear.

The pressure that splits the pipe builds between the ice and a closed faucet, not at the ice itself, which is why the break is often several feet downstream.

Where to look for a frozen or burst pipe

Freezing happens where pipes meet cold air, so search these first:

• Exterior walls, especially under kitchen and bathroom sinks on a north or windward side.
• Unheated spaces: crawl spaces, attics, garages, and unfinished basements.
• Hose bibs and outdoor spigots, plus the line feeding them.
• Anywhere air leaks in, such as a rim joist gap, a vent, or a pipe penetration.

Follow the line from the dead fixture back toward the water heater, feeling for the cold section as you go.

In a finished wall you cannot feel anything, so use the fixture that failed to narrow it to one run and look at the coldest point on that run.

Do not forget the lines nobody thinks about: the ice maker feed, a basement laundry sink, and irrigation backflow devices.

In a house on a well, check the pressure tank and the line from the pit, which often sit in the coldest corner of all.

What to do right now if it is frozen

Open the faucet that the frozen pipe feeds, hot and cold sides both. Melting water needs somewhere to go, and the open tap relieves pressure.

Apply gentle heat starting at the faucet end and working toward the frozen section, so meltwater can escape as it forms.

A hair dryer, a heating pad, warm towels, or a space heater kept clear of anything flammable all work.

Never use a blowtorch, propane heater, or any open flame. It is a fire risk and it can boil trapped water into a violent break.

Keep a phone and the main shutoff within reach the whole time, and watch the section as it releases.

Once flow returns, leave a slow stream running on that line overnight, since moving water is much harder to refreeze.

What to do right now if it burst

Close the main shutoff first. Everything else waits until the water stops.

Open the lowest faucets in the house to drain the lines and take pressure off the split.

Do not turn the water back on to test whether it is really broken. That question gets answered by the plumber, not by another few gallons through the wall.

Move what you can out of the wet area, and get air moving on the soaked material the same day.

The clock that matters now is mold, and it starts at roughly 24 to 48 hours of wet material sitting still.

If water reached outlets, cords, or the panel, cut the power to that area before you step into anything wet.

Then photograph everything before you clean, because a burst pipe claim is paid on documented damage.

The check to run after the pipe thaws

Flow coming back is not the end of it. The next hour is when a hidden split shows itself.

Run the recovered fixture for a few minutes and watch the pressure hold steady. A pulse that fades points to water escaping upstream.

Then repeat the meter test with everything closed. This is the reading that matters, because the ice plug is gone now.

Walk the rooms below and beside that pipe run, checking ceilings, wall bases, and the backs of sink cabinets.

Keep checking for 24 hours. Slow drips inside a wall take a day to reach a surface you can see.

A stain that appears the next morning is not a new leak. It is the same split, finally reaching the drywall.

If nobody is at the house

A freeze in an empty house is the expensive version, because nothing stops the water for days.

If you are away and suspect a freeze, get someone to close the main and open the taps rather than waiting to inspect it.

Leaving the heat at 55 degrees costs far less than one claim, and cabinet doors left open under exterior-wall sinks help more than people expect.

A water alarm near the water heater and under sinks costs about the price of a takeout meal and calls the flood in early.

When to call a plumber about a frozen or burst pipe

Call when you cannot find or reach the frozen section, which usually means it is inside a wall or under a slab.

Call when the pipe has not released after 30 to 45 minutes of steady, safe heat.

Call immediately if more than one line is dead, since that suggests a large frozen run or a break upstream.

Call if the pipe is galvanized steel or old polybutylene, both of which fail badly and often at the joints.

Once the plumbing is fixed, the drying job is separate work, and keeping the next freeze from doing this again is cheaper than either.

Keep reading

PreventionAt what temperature do pipes freeze?By CauseBurst pipe? What to do first, step by stepBy CauseHow to shut off the main water supply fastPreventionHow to prevent frozen pipes from burstingInsuranceDoes homeowners insurance cover a burst pipe?PreventionShould I let my faucets drip when it is below freezing?