The frigid weather during the upcoming winter months across our nation is likely to become the cause of extensive structural damage due to unprotected water pipes. Residential damage occurs from ruptures in pipes in which the water freezes, ultimately causing leakage or flooding in the home. Depending on the size of the fracture, a ruptured supply pipe can leak as much as 10,000 gallons of water per day. Large-loss leaks of this magnitude are not uncommon, especially when homeowners are away during extended periods of time.
The Principles of Frozen Pipes
It is most common for pipes to freeze between December and February due to the low outdoor temperatures. January is typically the coldest month across the nation, with an average temperature of 31 degrees Fahrenheit (1). The most common breaks that occur at this temperature are in hose bibs, irrigation systems, and other exterior piping.
Interior water pipes will not typically freeze until exterior temperatures fall below 20-degrees Fahrenheit. In northern states, water pipes can usually withstand even colder temperatures, a result of better building techniques such as installing piping in areas of the home that are more insulated. Construction methods in the south often overlook the possibility of frozen water pipes. In addition, homeowners in colder climates tend to be more aware of the potential for frozen water pipes and are also more proactive about preventative measures.
To prevent frozen pipes, the general recommendation is to apply adequate insulation or heat tape to pipes in exposed areas, such as within crawlspaces, attics, and garages, and to seal building envelope leaks that allow cold air into these confined spaces. During prolonged periods of extremely cold temperatures, it is a good habit to open vanity cabinet doors along the exterior walls. This limits the potential for pipes on the exterior walls to freeze by allowing warmer interior air to reach the piping. Another suggestion is to allow water to trickle from the faucets. The reason for this is two-fold: first, to relieve pressure buildup in the event that water begins to freeze within a pipe (thus allowing the developing ice crystals to safely expand axially along the length of the pipe) and second, to prevent freezing by drawing in relatively warmer water to replenish the system (depending on the volume of the trickle).
A freezing pipe is a multi-dimensional heat transfer problem. It is a function of the exterior temperature, interior temperature, pipe location, insulation, time and other factors. The heat within a system naturally dissipates until the system reaches the temperature of its surroundings. Water freezes within piping as heat from the water is transferred to the colder air. The water expands as it freezes and eventually forms a blockage within the pipe as it solidifies. The continued expansion of ice buildup increases the water pressure in the system.
Diagnosing freeze damage in piping assemblies is relatively straightforward because the failure occurs at the weakest location. When assembled correctly, soldered copper joints are stronger than the pipe; therefore, the pipe will tend to fail along the length of the pipe. A hairline fracture extending along the axis of the pipe indicates an over-pressurization which occurs as a result of freezing. Ice buildup and expansion creates a pressure buildup of the remaining water. The resultant pressure buildup of the water will eventually exceed the pressure limits of the pipe and effectively rupture it. Additionally, inadequate joints and certain valves may be weaker than the length of the pipe, thus failures may occur at these locations as well.
Winterization of Vacant Homes
When homeowners plan to be away from their home for extended periods during the winter, they often consider the lowest heat setting at which they can safely operate without causing damage. It is important to note that most homeowner’s insurance policies contain coverage exemptions relating to a failure to provide “adequate heat.” This provision does not indicate a specific temperature threshold, although a minimum of 55°F is a commonly used general reference.
Even though 55°F is commonly recommended, it does not seem to have an academic origin, especially considering the numerous variables involved in determining such a number. Temperatures within cabinets, wall cavities, and crawlspaces are much lower than the temperature recorded by an electronic thermostat in the middle of a heated room. When considering safe minimal thermostat settings, it is important to understand that every residential structure is unique and that it is impossible to assign a guarantee to any specific temperature recommendations.
If the heating system is going to be shut off at a vacant residence, it is imperative that the home is properly winterized. Winterization includes closing the main water supply valve to the building and purging the water from all of the water supply piping and plumbing appliances. Drains with P-traps should be cleared of water and filled with nontoxic antifreeze to prevent sewer gases from entering the residence.
Damages in the drainage system are typically not as severe as damages to the water supply system. Drain system freeze losses are typically less expensive because they result in less restoration. The water damage is limited to leakage from the water stored within the device, while the more significant cost lies within replacing the fixture itself. For example, if the water within a toilet bowl froze and cracked the bowl, there would be limited damage from the gallon of water in the bowl and the majority of the repair cost would be in replacing the toilet. On the supply side, the damage is much worse because if the main water valve is open, there will be a continuous leakage of water into the home. The pipe repair tends to be a minor cost (typically less than $100), while the resulting water damages can be tens of thousands of dollars (or more).
Investigative engineering firms are oftentimes retained to evaluate pipe freeze losses and determine whether or not “adequate” heat was provided within the residence. Many investigations of frozen water pipes reveal that the thermostat is in the “off” position, and sometimes homeowners will acknowledge that they turned the heat off. In one case, the homeowner admitted to turning the heat off but claimed that the ruptured pipe could not have been the result of a frozen pipe. The homeowner’s assertion that the pipe rupture was not a result of freeze damage was based upon a photograph taken after the pipe leak occurred. The photograph documented the electronic thermostat in the “off” position but showed that the room temperature was 48-degrees Fahrenheit. This photograph was taken during a mid-day site observation shortly after the discovery of the pipe leak. Alternatively, the freeze break occurred in a pipe that was located in an exterior wall cavity and likely had occurred when the exterior temperature was much colder than on the day of the site observation. In addition, the homeowner did not understand that the temperatures within exterior wall cavities tend to be much lower than those observed in the living space, or at the location of the thermostat.
The thermostat setting can easily be observed while inspecting a residence that has endured a freeze-ruptured water pipe. If the thermostat is switched “off,” then it is oftentimes a straightforward case; however, the homeowner might adjust the thermostat setting after the rupture in order to give the appearance that heat had been provided. It is also important to realize that some mercury switch thermostats can easily be adjusted out of level to lower the minimum temperature point. If the position of the thermostat is altered by rotating the wall assembly, the minimum allowable setting can be drastically reduced to a less-than-safe temperature. The most dependable method to determine whether or not heat was provided to a residence requires energy consumption calculations.
Case Study in Residential Energy Consumption
Another recently investigated case involved a pipe freeze break and subsequent water leak within a residence. The pipe break was observed within the kitchen cabinetry on the North exterior wall, a common area of freeze failure due to separation from the heat of the home. The home had been unoccupied for six months with monthly check-ins by the homeowner. It was previously unknown if the homeowner had turned on the heat during one of the monthly check-ins as the summer transitioned to fall and then winter. The engineer that investigated the case was able to perform an energy consumption calculation to determine if heat was provided. Invoices from the natural gas provider were used to evaluate natural gas usage for a specific period of time leading up to the pipe break.
The engineer was able to pinpoint the most likely day of the pipe rupture due to documented weather records in conjunction with the known date that the leak was first observed. The estimated date of failure from the weather records was consistent with the reported volume of water that had leaked for the duration of time that the pipe was ruptured. The rupture occurred almost a week prior to the discovery of the flood. The energy invoice for the month that included the day of the pipe failure was irrelevant because there was a spike in energy usage due to restoration efforts following the discovery of the flood. Upon entering the residence, the restoration company increased the thermostat setting to amplify the interior heat and assist the dehumidifiers and fans in drying the structure. Invoices for several months prior to the pipe freeze provided the key information.
Energy bills indicate the natural gas consumed during a given billing period in a unit of “therms”. (One therm is equal to 100,000 British Thermal Units, or BTUs.) In this case, an evaluation of therm usage for invoices dating back six months from the time of the freeze indicated that the heat had been turned on in the late fall, approximately two months prior to the time of the pipe freeze. Invoices from the summer months indicated zero therm usage since the electric water heater does not consume natural gas and the oven and range was not in use. Therm usage consistent with a furnace pilot light was evident on invoices beginning in the late fall, with clear indications that the furnace was not operating regularly. Despite some heat supplied to the residence, the pipe freeze occurred in a confined space near an exterior wall during an extended period of subzero temperatures.
Claims and Potential Liability
Water leaks from frozen water pipes result in significant losses each year, second only to hurricanes in terms of both the cost of the claims and the number of damaged homes (2). Although some insurance companies do not officially recognize frozen water pipes as a “catastrophe”, insurers across the nation share the burden of these incredible monetary losses.
Property owners and managers may be responsible for damages that result from a pipe rupture and the subsequent leakage in an unheated (or inadequately heated) building. The resulting water damage can be extremely costly to repair when, in most cases, pipe freezing is completely preventable with winterization techniques.
Test your claims knowledge – Question and Answer Session
- A. What is the lowest possible heat setting that will absolutely prevent a pipe from freezing within a building?
- B. 20-degrees Fahrenheit.
- C. 33-degrees Fahrenheit.
- D. 55-degrees Fahrenheit.
- E. The temperatures listed above will not absolutely prevent a pipe freeze.
ANSWER: D. Although many experts recommend a 55-degree minimum, this recommendation does not have academic origin. Every structure is unique in terms of the placement of pipes, insulation, thermostat location, and many additional factors. It is better to be safe than sorry as turning the heat down in search of the lowest possible heat setting can result in pipe freeze breaks which lead to costly repairs.
- (Reference graphic below) Assuming that there are 6-inches of fiberglass insulation both above and below the water pipe pictured running through the attic, the heated interior space is 70-degrees Fahrenheit, and the unheated attic space is minus 10-degrees Fahrenheit. What is the temperature at the waterpipe?
ANSWER: 30-degrees Fahrenheit. You can simplify the heat transfer problem and take the average of the two temperatures.
- (Reference graphic above) Is the answer to question 2 (temperature) cold enough to cause a pipe to freeze and rupture?
ANSWER: Yes. 30-degrees Fahrenheit is cold enough to cause a freeze break because it is below the freezing point of water. Although not typical, if given enough time, a water pipe would eventually freeze break if exposed to a long enough period at this temperature.
- What is the coldest month on average in the United States and is the average temperature of this month cold enough to freeze and rupture water pipes?
ANSWER: January is the coldest month with an average temperature, 31-degrees Fahrenheit, cold enough to cause freeze breaks. 31-degrees Fahrenheit is below the freezing point of water. Although not typical, if given enough time, a water pipe would eventually freeze break if exposed to a long enough period at this temperature.