January 29, 2019

Burst pipes can be a major cause of property damage, especially after a bout of extreme weather.  It is a common misconception that pipes burst because the water inside the pipe freezes and then expands. What really causes burst pipes, how can this be avoided and what action should be taken if you suspect a burst?

Pipes burst in freezing climates because the water inside the pipe freezes and this creates a dam effect. Some materials, such as Pex piping, are designed to be able to withstand expansion better than standard plastic and metal but they will still have their limits. When water is unable to pass because of the expansion of ice, pressure builds and eventually the pipe bursts at its weakest point, releasing the pressure which can often involve hundreds, if not thousands of gallons of water. 

The weakest point may be exceptionally weak (where it should have been able to withstand the pressure) or it may be commonly weak (due to joints or connections which are naturally weaker than the pipes themselves).  Contributing factors often lead to weak points in piping and this can include improper installation, corrosion, or manufacturer’s defect.

Improper installation

Improper installation can create immediate weaknesses in the piping and joints or lead to corrosion that over time weakens the system. These can appear similar to issues resulting from a manufacturer’s defect in an area of piping.

One case where our forensic engineers were called upon to investigate loss causation involved a burst sprinkler system within an eight-story building that was under construction. Our expert noted that only the sprinkler joints and head on the second floor burst, while the others remained intact. Upon investigation it was established that the contributing cause was faulty installation within the second floor, which led to phase change expansion fractures in the joints, elbows and sprinkler heads


Corrosion is perhaps the most commonly seen cause of weakness, specifically in copper piping.  According to the Foundation of Water Research, copper inherently has protective films which get broken down by water that has a high pH (often referred to as ‘hard water’). However, this is not the only cause of corrosion: biofilms, a film housing bacteria inside the pipe is commonly found in hospitals and healthcare facilities; flux residues left in the pipe after installation or as a result of manufacturers defect; and erosion can be caused by high velocity or changing direction of water movement.

When the pipe is corroding it is called ‘cuprosolvensy’, which means the dissolution of the copper surface.  Cuprosolvensy becomes visible in the exterior of the pipe when white or blue growth develops, indicating weakened areas of the pipe (pinholes) or around the c-joints.  If the corrosion occurs in the pipe itself, a pinhole may develop, which is visible from the outside of the pipe.

If the area of piping is unavailable for visual inspection, looking below and around the pipe will often reveal evidence that a pinhole leak existed in that area.  Water stains, fungus, mold and blistering, on the surfaces under the pipe indicate ongoing moisture, or a slow leak.

In newly constructed plumbing, an indication that corrosion is occurring typically manifests itself early on, as water may come out of the tap with a blue-ish hue and can taste metallic.  Eventually, the white or blue build up will become evident on the exterior of the copper pipes (at the pinhole or at the joints) and even sometimes around the taps.

Freezing Temperatures

The building envelope, building insulation, piping insulation, piping materials, indoor and outdoor temperatures and duration of those temperatures are all factors leading to pipe freeze, which leads to burst.

In a recent pipe freeze investigation of a “frost free” spigot in an apartment building under construction, our engineer was asked to investigate pipe which appeared to have burst due to freezing, however the inside temperatures were allegedly set to 45 F. Our engineer’s inspection found that frost free spigot had been used, the piping and insulation were in excellent condition and had been installed correctly and there were no signs of manufacturing defects. So why did it burst?

It was found that the heating and ventilation system had been set 45 F but in the ‘cool’ position, rather than in the ‘heat’ position, so it was actually not providing an adequate amount of heat required considering the duration of the freezing temperatures on the date of loss.


There are many ways to prevent burst pipes. Here we consider six key prevention methods:

  1. If there is any piping in an area of the building that may reach temperatures below 40 F, leave the faucet valves slightly open.  Allowing a slow and steady drip will reduce the pressure that would otherwise be created by an ice dam.
  2. Building and pipe insulation – although this alone will not always prevent freeze, it will delay it.  The building envelope, amount and distribution of the insulation in the building must be considered and there are several methods and materials used for insulating including R-value/heat transfer, fiberglass insulation, natural insulation and foam insulation.  Methods employed include box in methods, tent insulation or roof line and foam insulation.
  3. If a property is vacant or temporarily not in use check to ensure that the heating system is properly set and that it has adequate reserves. If the property is completely vacant and there is no use for water, then the most obvious and complete method of preventing a burst pipe is to turn the water off at the main and open all faucets, allowing them to flow until empty and leaving them open until the water is turned back on again. Supply lines are the source of the most significant water damage during pipe freeze as they are bigger with more volume accumulation.
  4. Develop a procedure to respond to loss of heat or electricity by identifying areas of the property that lose heat quickly and install a thermostat there so that you can ensure it remains above 40 F.
  5. Service heating systems regularly and check windows and doors to ensure there are no openings or breaks.
  6. Be aware that pipes are most susceptible to freezing when located in an outside wall, under a sink on an outside wall, and in an unheated crawlspace.

How long does it take for water in a pipe to freeze?

This technical question is answered in the National Fire Protection Association white paper in the ASHRAE 2005 Handbook, Chapter 26:

Assuming that water is not flowing the time it takes for water to freeze in a pipe that is wrapped in a normal pipe insulation jacket, is given by the following equation:  ? = ?(?12)2??ln ?? – ?? ?? − ??

Where: θ =time to freezing (h); ρ = density of water (62.4lb-F); C pie=specific heat of water (1.0Btu/lb-F); D1=inside diameter (ft); RT=combined thermal resistance of pipe wall, insulation, exterior air film (for a unit length pipe); ti=initial water temp (F); ta=ambient air temp (F); tf=freezing temp (F); and ? = ?(?12)2??ln ?? – ?? ?? − ??.

The first signs of a ‘frozen’ pipe – reduced flow or no flow at a plumbing fixture

  1. If you experience a “no flow” situation:
    • Turn off the main water valve and leave the faucets open. Remember, however, that if the water is shut off at the main, it may also turn off fire protection systems.
    • Do not use any open flame to attempt to thaw the pipes.
    • Do not use an electric heater, electric hair dryer, etc. applied directly to the piping as any leaking water may cause electrocution.
    • Turning the water back on is best handled with two people. One person turning on the water slowly and the other walking about the building to be sure no water is running.
  2. Often heat and patience is the best way to get the pipes to thaw. We do, however recommend that if a freeze occurs, find the source (insulation, temperature, etc) and correct it so it will not happen again. Note that the pipe(s) that have frozen may already be fatigued and would now be classified as ‘exceptionally weak’, which means they may be more disposed to bursting on the next freezing occasion.
  3. If water is escaping, turn off the main water valve immediately and open the all hot and cold faucets.