Heating baseboard freeze damage leak (C) Daniel FriedmanFreezing water pipe or plumbing drain pipe burst & leak patterns
Freeze damage in plastic & metal supply & pipes

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How & where do pipes burst when they freeze? This article describes the different ways in which plumbing pipes freeze & burst & about the pipe burst variations by different piping materials. We illustrate several burst pipe patterns for copper water supply piping and include photographs of the different failure modes for plastic pipes & for galvanized iron water pipes.

In a second section we illustrate breakage patterns when plastic, galvanized iron, or cast iron drain piping freezes. Our page top photo illustrates that hot water heating pipes in a building can freeze and burst or separate when heat fails or is turned too low.

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Guide to Patterns in Which Water or Drain Pipes Burst or Leak due to Freeze-Ups & Ice Pressure

Frozen pipe burst pattern closeup (C) Daniel Friedman

Freeze or Frost Damaged Copper Piping Break Patterns

Our photo (left) provides a close up showing one of several patterns in which a copper water pipe will swell and burst due to freezing.

In this common copper pipe freeze and burst pattern pressure from expanding ice in the copper line is localized to a specific point, sometimes further obstructed by a pipe elbow or valve.

Pressure from expanding ice forms a round bulge in the copper that bursts in the pattern shown in our photos.

Learning to recognize the typical locations and patterns in which building pipes from any system (water supply, drains, hot water heating system) burst can help diagnose previous troubles as well as prevent future freeze-ups, burst piping, and costly mold or water damage cleanup projects.
Frozen pipe burst damage pattern by joint separation (C) Daniel Friedman

Our pipe-freeze damage photo at left illustrates a different way in which water supply piping can burst or leak due to freezing. In this case the force of expanding ice in the water pipe did not cause the copper pipe to swell nor crack.

Rather the ice pressure along the length of the pipe or between the solder joint and a nearby obstruction formed by an elbow or valve caused horizontal movement that separated the sweat fitting, opening the pipe ends.

Watch out: the copper pipe bulges, splits, separations and damage describe here can occur on hot water heating system piping too (see our page top photograph) if the heat is left off in a building. You can avoid frozen heating pipes in a shut-down building by draining the heating system when it is shut down (WINTERIZE - HEAT OFF PROCEDURE), or by providing a proper antifreeze mixture in the boiler and heat piping. (ANTIFREEZE for BOILERS).

Frozen pipe split pattern (C) Daniel Friedman

At AIR BLEEDER VALVES we describe opening air bleeders to remove trapped air in heating piping; but that procedure can also assist in deliberate drain-downs of heating system piping as well.

The pipe frost damage shown in this photo illustrates another pipe damage pattern: splitting. The pressure of ice expanding in a length of piping can cause the pipe to expand and split along the length of the pipe.

Depending on how pipe was manufactured as well as on the location and distribution of expanding ice in the length of pipe, some pipes may tend to split when freezing while others will bulge and burst and still others may leak by separation at solder joints or connections.

Watch out: when turning water back on in a building that was left with heat off, regardless of whether or not pipes were drained, be alert for a surprise spray of water from a burst water supply or heating pipe that you did not see at initial inspection as part of your de-winterizing procedure. (DE-WINTERIZE a BUILDING).

Galvanized iron water supply piping (C) Daniel Friedman

Never just turn heat and water back on and leave the building. Make a complete visual inspection for obvious leaks, listen for leaks in wall, ceiling, or floor cavities, and even if no leaks are found, inspect the building again in 24-hours or less to check for small leaks that are slow to show-up.

Leaving a building wet for more than 24-48 hours risks not only costly water damage but a still more costly mold remediation clean-up job.

Galvanized iron water supply pipe can also burst from freezing, and may split at seams depending on how the pipe was manufactured.

Galvanized iron water supply (or drains) are more likely to burst by splitting or fracturing if pipe sections are corroded from an external cause such as corrosive water or by contact with materials or surfaces that increase the pipe corrosion rate.

Our photo (above-left) illustrates a galvanized iron pipe failure (and replacement) at a spa in Lourdes, Mexico.

Drain Pipe Freeze & Burst Patterns Organized by Drain Pipe Material

Cast iron drain cracking (C) InspectApedia

Cast iron drain piping freeze damage

Cast iron drain pipes damaged by freezing often fracture as our PVC example or pipes may split at cast-joints. The cast iron drain in our photo above was located beneath a basement floor - and failed by cracking as shown in the image.

Watch out: the crack in a cast iron pipe that causes the drain to leak may be on a side of the drain that you cannot see, such as its under-side along the floor, or a pipe side against a building wall. That's why above we warned of the importance of a careful inspection when a building is being de-winterized.

The cast iron drain (now removed at this location) split along a seam when it froze; often cast iron piping will break into fragments if the piping is filled with water and is frozen solid.

Galvanized iron drain pipe (C) Daniel Friedman

Plastic ABS & PVC drain pipe freeze or frost damage

Building drain clog (C) Daniel Friedman

The photo above shows remains of a PVC drain line that froze and burst in an un-heated crawl space.

This burst pattern is most typical of above-ground and some below-ground PVC drain pipe freeze burst damage - the material fractures.

ABS plastic piping also fails by cracking, discussed as a product failure independent of freezing, at PLASTIC PIPING

Watch out: burst drain piping that spills sewage in a building is going to require not just mopping up but disinfecting or sanitizing of the affected areas. Even dust from areas where there was a previously inadequately cleaned sewage spill can carry pathogens into the building air and into other building areas from that of the original sewer backup or burst pipe spill.

Building drain clog (C) Daniel Friedman

The most common cause of drain line freeze-bursting is the combination of

  1. A blocked plumbing drain line - the line sits full of wastewater
  2. The drain line is exposed to freezing - because drain lines are not normally expected to be filled with water, drains are not always protected from freezing at all locations in the piping runs.
  3. Slow running water, leaks or drippy faucets: A third cause of frozen and burst drain piping is important but less obvious: a dripping faucet or a toilet that runs can send a slow trickle of water down a drain line leading to freezing or even a burst drain pipe in an un-heated crawl space, basement, or outdoors where a building drain may be above the frost line.

Frozen drain piping prevention, burst building drains: how to prevent freezing drain piping, watching for leaks and slow drips into drain systems are discussed at Drain Pipe Protection.

Reader Question: hot water thermal shock cracks ABS drain in very cold climate?

I live above 5 garages in a town home community. The homes were built around 1978. Between my shared garage side-wall there is a drain pipe that goes from my kitchen and connects to a common drain line about 18” into the ground. The problem has happened twice now and it currently needs repair.

It cracks when I run hot water from my kitchen sink when it is cold out. I had it repaired 2 years ago and last winter it was very cold in Minnesota and I forgot to open my cupboard door to allow warmer air to try and prevent this problem.

It is very difficult to even look at the drain pipe to see where the crack is but I know it leaks because the sheetrock has some black mold from the water leaking out of the crack and it makes quite a loud noise when I run hot water down my sink. I am hoping there is some way to insulate or heat this ABS pipe (maybe use some other type of pipe) so when I have it repaired, it won’t crack again. The most recent quote I got was a couple of months ago for about $1400.00. - Anon. by private email, 2016/01/19


I was surprised to read about cracking ABS drain piping just in response to thermal shock. Usually I find the problem of cold weather damage to ABS drains is traced to a slow drain, freezing and ice-pressure bursting or cracking of the drain.

Stressing of the piping from improper routing or support can also cause such cracks.

Where exposed to sunlight, photo-oxidation also leads to ABS pipe failures.

I would certainly be reluctant to spring for a repair before we are confident that we understand the problem and thus agree on how it's to be solved.

I tried a google scholar search for research citing thermal shock causing cracks in ABS drain piping and found no clear citation pointing to damage from thermal shock to cold ABS drains caused by residential hot water drainage. There was some related research that I cite below: (Search argument: thermal shock damage to ABS pipe)


Galvanized Iron drain pipe freeze damage

Galvanized iron pipe can also burst from freezing, and ma


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