Frozen & Burst Pipe Investigations Expert Article

When pipes freeze and burst releasing water, the mechanical engineers at Robson Forensic are frequently retained to determine the cause of the failure. This article provides a starting point for frozen and burst pipe investigations.

Frozen & Burst Pipe Expert Witness Investigations

Frozen & Burst Pipe Investigations

The water in pipes can freeze when they are exposed to temperatures below 32°F for an extended period of time. Frozen pipes occur for two basic reasons:

  1. Installation of pipes in an unheated space without adequate protection -or-
  2. Insufficient heat in the area of the freeze

Domestic water piping, HVAC heating and cooling piping, irrigation piping, and fire protection piping are all susceptible to damage from freezing. Both plastic and metal pipes can burst when they freeze. Dependent on pipe size and system pressure, a small crack in a burst pipe can spew hundreds or even thousands of gallons of water in a day, causing flooding and property damage, and the potential for mold.

In the course of these investigations, there are common questions that need to be addressed involving system design, installation, maintenance, and operation.

Why Pipes Burst

When water freezes, it expands. That is why a can of soda will burst in your freezer. When water freezes in a pipe, it expands in the same way.

When a pipe bursts, the break does not necessarily occur at the exact spot where the ice blockage is located. Ice expansion will exert pressure against the pipe wall but also pressurizes the water trapped between the ice and a closed valve or fixture. As the water continues to freeze and expand inside the pipe, it causes the trapped water to continue to increase in pressure. The increased water pressure may cause a pipe to burst or a sprinkler head to release in a location where there is no ice blockage.

Frozen & Burst Pipe Expert Diagram

System Design & Installation

A few common locations where pipes freeze are: outdoor hose bibs, swimming pool supply lines, fire protection lines, and water supply pipes in unheated interior areas, including basements, crawlspaces, attics, garages, bathroom sink cabinets, and kitchen cabinets. Pipes that are along exterior walls that have little or no insulation, voids in the insulation or improperly installed building wrap are also subject to freezing. 

The National Fire Protection Association (NFPA) requires that wet (water-filled) fire protection systems be designed, installed, and maintained at a temperature above 40°F to prevent the risk of freezing. 

The International Plumbing Code (IPC) requires pipes to be protected from freezing:

“305.6 Freezing. Water, soil and waste pipes shall not be installed outside of a building, in attics or crawl spaces, concealed in outside walls, or in any other place subjected to freezing temperature unless adequate provision is made to protect such pipes from freezing by insulation or heat or both. Exterior water supply system piping shall be installed not less than 6 inches (152 mm) below the frost line and not less than 12 inches (305 mm) below grade.”

Building owners can take precautions to prevent frozen pipes

There are several preventive steps that building owners can take to prevent pipes from freezing, including the following:

Before the cold weather sets in:

  • Ensure heating equipment has been serviced, is operational, and has been turned on.
  • Be sure that thermostats are set high enough so that all areas of the building where piping is located are at temperatures above freezing.
  • Verify that pipes in unheated spaces have some form of freeze protection such as antifreeze, electric heat tape, constantly moving water, etc.
  • Disconnect garden hoses, and if possible, use an indoor valve to shut off and drain water from pipes leading to outside faucets. Keep the outside valve open so that any water remaining in the pipe can expand without causing the pipe to break. Exterior garden hoses that are left attached to outside faucets can cause the pipe to freeze within the wall.
  • Seal leaks that allow cold air inside near where pipes are located. Look for air leaks around wall penetrations for electrical wiring, dryer vents, and pipes, and use caulk or insulation to keep the cold air out. With severe cold and wind, even a tiny opening can let in enough cold air to cause a pipe to freeze.
  • Have fire protection system inspected per NFPA 25 before the onset of cold weather.

When cold weather is expected:

  • A trickle of hot and cold water might be all it takes to keep pipes from freezing. When the weather is very cold outside, let the water drip (at a minimal amount) from the faucet served by exposed pipes. A hot water supply line can freeze just as a cold water supply line can freeze.
  • During extreme cold, keep the thermostat set to the same temperature both during the day and at night, rather than turning down the heat while sleeping. Further drops in the temperature – more common overnight – can catch homeowners off guard and freeze pipes.
  • Open kitchen and bathroom cabinet doors to allow warmer air to circulate around un-insulated pipes near outside walls.
  • Keep garage doors closed if there are water supply lines in the garage.

If away from home for an extended period of time:

  • When a building is unoccupied, the safest way to prevent damage from frozen pipes is to shut off and drain the water system. The main water valve should be turned off and all faucets opened to let the water out of the pipes. Plumbing fixtures should be drained or filled with non-toxic anti-freeze. Drain irrigation and swimming pool supply lines as well. Be aware that if there is a fire protection system in the building, it may be deactivated when the water is shut off.
  • If away from home during cold weather, leave the thermostat set high enough so that the water in the coldest pipe stays above freezing, which is 32°F. The thermostat reading is not necessarily the temperature in the coldest area of the building. Thermostats can only measure the temperature of the room they are in. Freezing of water pipes is most likely to be along the exterior walls and in unheated locations.
  • Ask a friend or neighbor to check inside the house on a daily basis to ensure that the heat is working and keeping the house warm enough to prevent freezing.
  • Use temperature monitors that can send alerts if temperature in the building drops below a certain level which will indicate the heat is not working.

Does the insurance policy cover the loss?

Insurance companies may deny claims resulting from frozen pipes if:

  • The property was unoccupied and the insured party did not maintain heat in the building or shut-off all water and completely drain the piping systems and equipment.
  • If a small crack in a water pipe causes slow leakage over an extended period, the resulting damage may not be covered. This could be considered a maintenance issue instead. Water losses that occur due to lack of maintenance are typically not covered on a standard homeowner’s policy.
  • Fire protection systems froze due to changes in the HVAC system or changes in the room layout.

Considerations When Investigating Frozen Pipe Failures

  • Was heat and/or electricity maintained at the building?
  • If the building was unoccupied for an extended period of time, did the building owner shut off the main water valve and drain the plumbing system of water?
  • Was the thermostat set high enough to maintain temperatures above freezing in all areas of the building?
  • Was the heating system switched off at the thermostat, a disconnect switch at the equipment, or a circuit breaker?
  • Did the building owner make arrangements for someone to check inside the house on a daily basis to ensure that the heating system was operating and keeping the building sufficiently warm?
  • Is the burst piping located in an unheated space? If so was it protected?
  • Was the area or piping system properly insulated?
  • Should an alternative design have been used for the fire protection system?

Other considerations:

  • An analysis of the heating fuel usage and outside temperatures during the freeze incident can be compared to the amount of heating fuel consumption required to maintain heat in the building.
  • An analysis of utility bills can determine if the heating system was operating during the freeze incident as well as the time periods leading up to the incident. The fuel bills can be used to distinguish between heating of domestic water and space heat.

Building Systems Investigations

Building systems refers to the mechanical (HVAC), electrical, and plumbing systems found in modern buildings. Our experts are frequently engaged in cases involving design and installation errors, product malfunctions, as well as maintenance and operations issues.

For more information visit our Building Systems practice page.

Featured Expert

Ronald J. Natoli, Mechanical Engineer & Building Systems Expert

Ronald J. Natoli, P.E., C.F.E.I.

Mechanical Engineer & Building Systems Expert
Ron is a Mechanical Engineer with over 30 years experience in the design, construction, startup, control, and commissioning of mechanical, fire protection, plumbing and process systems. Ron held… read more.


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