Pipe Freeze Basics
Pipe freezes result in countless water-related property losses each year. While the cause and circumstances surrounding pipe freezes may ostensibly appear obvious, there are numerous misconceptions which raise questions and create confusion. Determining the cause of a pipe freeze can even be quite complicated when dealing with industrial process or HVAC piping and related control systems.
What Happens When Water Freezes in a Pipe?
Let us begin with the basics before diving into some of the more common misconceptions. When referring to a pipe freeze, we are talking about the water within a pipe freezing due to exposure to cold temperatures, often resulting in a deformed or broken pipe.
This damage to the pipe is caused by the expansion of the water as it freezes. Anybody who has placed ice in a glass to cool a drink has surely noticed that the ice always floats to the top. Water is most dense at 39.2°F (4°C), but then decreases in density as it cools to its freezing point of 32°F (0°C). In other words, as water approaches its freezing point, it expands. More specifically, it expands by about 9%.
How Does Frozen Water Affect a Pipe?
As the temperature of water approaches freezing, ice crystals begin to form. In colloquial terms this takes on the appearance of ‘slush.’ By this point, the water is already expanding. If contained within a rigid pipe, the pressure within the pipe will rise. If the pressure in the pipe exceeds the physical strength of the pipe, the pipe will deform or even burst. Typically, a pipe will burst at areas of stress concentrations, such as pipe bends or elbows.
In some cases, the rise in pressure may cause the pipe to burst while still in the slush stage, before solid ice forms. This typically results in an immediate leak. At other times, solid ice forms in a portion of the pipe before an adjacent portion fails. In such cases, a small amount of water/slush leaks from the pipe, while the solid ice upstream plugs the pipe and prevents the flow of water. In these instances, it is not until days later when the cold weather passes and the ice within the pipe melts that the leak is apparent.
For this reason, it is advised that if a section of pipe is suspected to have been exposed to freezing temperatures, a thorough inspection of the piping system in the suspected area should be conducted immediately. Discovery of a pipe failure prior to thawing of the ice within a damaged pipe may prevent catastrophic water damage to the building.
What Is the Role of Pipe Insulation?
When reporting after site inspections of freeze damaged pipes, I am often asked whether the pipes were insulated. In many instances, given this question in the context and site conditions of the loss, it is apparent that the intent and effect of pipe insulation is not widely understood.
In general, insulation is used to slow the rate that heat transfers from one thing to another. It is also worth noting that heat only travels from high temperature to low temperature. Therefore, it is not a matter of the cold getting into a pipe to freeze it, but rather the heat leaving the pipe.
Pipe insulation is most beneficial when a constant or intermittent flow of temperature conditioned water passes through the pipe. For instance, if building heating system water is flowing through a pipe to deliver water to a heating coil, insulating the pipe would prevent the hot water within the pipe from losing its heat energy to the air surrounding the pipe. However, in the case of a fire sprinkler pipe, there is no flow of water unless there is a fire. There is no source to provide heat energy to the stagnant water within the pipe. If such a pipe is exposed to freezing temperatures, it is only a matter of time before the pipe will freeze, with or without insulation. A similar example is a plumbing supply pipe, wherein the water may be stagnant during overnight hours when restrooms and other fixtures are not in use.
What About Building Insulation?
Building insulation can be vital to protecting pipes from freezing. Of equal importance is the placement of building insulation with respect to piping. Keep in mind that insulation is intended to slow the flow of heat transfer from areas of high temperature to areas of lower temperature. In the case of a building in the winter months, the high temperature exists in the conditioned interior of the building and the lower temperature is outside. To protect pipes from freezing, building insulation should be placed between the piping and the building exterior. If building insulation is placed between the building interior and the piping, the insulation would prevent the building heat from protecting the pipes from freezing.
In many instances, I see buildings with roof insulation and supply plumbing or fire sprinkler piping in the space between the roof insulation and the lay-in ceiling below. The building insulation is appropriately placed with respect to the piping to allow the heat from the building interior to heat the piping. Unfortunately, at some later point in time, insulation was added to the top side of the lay-in ceiling to prevent noise transfer between rooms via the ceiling space. The new insulation was placed between the building interior and the piping, thereby slowing the rate at which heat is transferred from the building interior to the space above the ceiling, increasing the risk of a pipe freeze.
Can Moving Water Freeze?
In the southern states, many say that you should let just a bit of water run from a faucet or two during the nights of a cold spell to prevent the pipes in the crawl space from freezing. Does this really work? The answer is, yes, but not for the reason most people think. A common misconception is that moving water will not freeze. Obvious cases against this notion are frozen rivers or even water falls which commonly occur in extremely cold climates. The reason that running water from a faucet prevents freezing is because the water coming from the pipes below ground is relatively warm. As the water flows through the piping above ground, it begins losing its heat to the surrounding cold air. The pipes will be prevented from freezing as long as the flow of water is fast enough to carry the water through the crawl space and into the house before it loses enough heat to freeze.
Another illustration of this is the failure of a heating coil I inspected in an air-handling unit at a medical facility. The coil piping was such that when there was no call for heat, the control valves would divert heating system water away from the coil. The residual water in the coil would remain stagnant unless cold air temperatures within the air-handling unit triggered the freeze protection controls sequence of operation which activated the coil’s recirculation pump. However, the designer failed to cause the control valve to open to allow heating system water into the coil piping loop. Only the small amount of residual water in the coil and associated branch piping were recirculated through the coil to prevent freezing. Despite the high flow rate of the water through the coil, the water soon cooled to near freezing and the coil burst.
As discussed above, a proper investigation into a pipe freeze failure must consider the pipes as part of the overall building system. Building codes and industry standards should be examined when evaluating piping system installations. Improper system operation can also be a contributing factor to the circumstances that lead to failures. Often, extensive experience and a solid understanding of system fundamentals are the best tools in determining the root cause of pipe freeze failures.
Pipe freezes result in countless water-related property losses each year. While the cause and circumstances surrounding pipe freezes may ostensibly appear obvious, there are numerous misconceptions which raise questions and create confusion. Determining the cause of a pipe freeze can even be quite complicated when dealing with industrial process or HVAC piping and related control systems.
What Happens When Water Freezes in a Pipe?
Let us begin with the basics before diving into some of the more common misconceptions. When referring to a pipe freeze, we are talking about the water within a pipe freezing due to exposure to cold temperatures, often resulting in a deformed or broken pipe.
This damage to the pipe is caused by the expansion of the water as it freezes. Anybody who has placed ice in a glass to cool a drink has surely noticed that the ice always floats to the top. Water is most dense at 39.2°F (4°C), but then decreases in density as it cools to its freezing point of 32°F (0°C). In other words, as water approaches its freezing point, it expands. More specifically, it expands by about 9%.
How Does Frozen Water Affect a Pipe?
As the temperature of water approaches freezing, ice crystals begin to form. In colloquial terms this takes on the appearance of ‘slush.’ By this point, the water is already expanding. If contained within a rigid pipe, the pressure within the pipe will rise. If the pressure in the pipe exceeds the physical strength of the pipe, the pipe will deform or even burst. Typically, a pipe will burst at areas of stress concentrations, such as pipe bends or elbows.
In some cases, the rise in pressure may cause the pipe to burst while still in the slush stage, before solid ice forms. This typically results in an immediate leak. At other times, solid ice forms in a portion of the pipe before an adjacent portion fails. In such cases, a small amount of water/slush leaks from the pipe, while the solid ice upstream plugs the pipe and prevents the flow of water. In these instances, it is not until days later when the cold weather passes and the ice within the pipe melts that the leak is apparent.
For this reason, it is advised that if a section of pipe is suspected to have been exposed to freezing temperatures, a thorough inspection of the piping system in the suspected area should be conducted immediately. Discovery of a pipe failure prior to thawing of the ice within a damaged pipe may prevent catastrophic water damage to the building.
What Is the Role of Pipe Insulation?
When reporting after site inspections of freeze damaged pipes, I am often asked whether the pipes were insulated. In many instances, given this question in the context and site conditions of the loss, it is apparent that the intent and effect of pipe insulation is not widely understood.
In general, insulation is used to slow the rate that heat transfers from one thing to another. It is also worth noting that heat only travels from high temperature to low temperature. Therefore, it is not a matter of the cold getting into a pipe to freeze it, but rather the heat leaving the pipe.
Pipe insulation is most beneficial when a constant or intermittent flow of temperature conditioned water passes through the pipe. For instance, if building heating system water is flowing through a pipe to deliver water to a heating coil, insulating the pipe would prevent the hot water within the pipe from losing its heat energy to the air surrounding the pipe. However, in the case of a fire sprinkler pipe, there is no flow of water unless there is a fire. There is no source to provide heat energy to the stagnant water within the pipe. If such a pipe is exposed to freezing temperatures, it is only a matter of time before the pipe will freeze, with or without insulation. A similar example is a plumbing supply pipe, wherein the water may be stagnant during overnight hours when restrooms and other fixtures are not in use.
What About Building Insulation?
Building insulation can be vital to protecting pipes from freezing. Of equal importance is the placement of building insulation with respect to piping. Keep in mind that insulation is intended to slow the flow of heat transfer from areas of high temperature to areas of lower temperature. In the case of a building in the winter months, the high temperature exists in the conditioned interior of the building and the lower temperature is outside. To protect pipes from freezing, building insulation should be placed between the piping and the building exterior. If building insulation is placed between the building interior and the piping, the insulation would prevent the building heat from protecting the pipes from freezing.
In many instances, I see buildings with roof insulation and supply plumbing or fire sprinkler piping in the space between the roof insulation and the lay-in ceiling below. The building insulation is appropriately placed with respect to the piping to allow the heat from the building interior to heat the piping. Unfortunately, at some later point in time, insulation was added to the top side of the lay-in ceiling to prevent noise transfer between rooms via the ceiling space. The new insulation was placed between the building interior and the piping, thereby slowing the rate at which heat is transferred from the building interior to the space above the ceiling, increasing the risk of a pipe freeze.
Can Moving Water Freeze?
In the southern states, many say that you should let just a bit of water run from a faucet or two during the nights of a cold spell to prevent the pipes in the crawl space from freezing. Does this really work? The answer is, yes, but not for the reason most people think. A common misconception is that moving water will not freeze. Obvious cases against this notion are frozen rivers or even water falls which commonly occur in extremely cold climates. The reason that running water from a faucet prevents freezing is because the water coming from the pipes below ground is relatively warm. As the water flows through the piping above ground, it begins losing its heat to the surrounding cold air. The pipes will be prevented from freezing as long as the flow of water is fast enough to carry the water through the crawl space and into the house before it loses enough heat to freeze.
Another illustration of this is the failure of a heating coil I inspected in an air-handling unit at a medical facility. The coil piping was such that when there was no call for heat, the control valves would divert heating system water away from the coil. The residual water in the coil would remain stagnant unless cold air temperatures within the air-handling unit triggered the freeze protection controls sequence of operation which activated the coil’s recirculation pump. However, the designer failed to cause the control valve to open to allow heating system water into the coil piping loop. Only the small amount of residual water in the coil and associated branch piping were recirculated through the coil to prevent freezing. Despite the high flow rate of the water through the coil, the water soon cooled to near freezing and the coil burst.
As discussed above, a proper investigation into a pipe freeze failure must consider the pipes as part of the overall building system. Building codes and industry standards should be examined when evaluating piping system installations. Improper system operation can also be a contributing factor to the circumstances that lead to failures. Often, extensive experience and a solid understanding of system fundamentals are the best tools in determining the root cause of pipe freeze failures.
Pipe freezes result in countless water-related property losses each year. While the cause and circumstances surrounding pipe freezes may ostensibly appear obvious, there are numerous misconceptions which raise questions and create confusion. Determining the cause of a pipe freeze can even be quite complicated when dealing with industrial process or HVAC piping and related control systems.
What Happens When Water Freezes in a Pipe?
Let us begin with the basics before diving into some of the more common misconceptions. When referring to a pipe freeze, we are talking about the water within a pipe freezing due to exposure to cold temperatures, often resulting in a deformed or broken pipe.
This damage to the pipe is caused by the expansion of the water as it freezes. Anybody who has placed ice in a glass to cool a drink has surely noticed that the ice always floats to the top. Water is most dense at 39.2°F (4°C), but then decreases in density as it cools to its freezing point of 32°F (0°C). In other words, as water approaches its freezing point, it expands. More specifically, it expands by about 9%.
How Does Frozen Water Affect a Pipe?
As the temperature of water approaches freezing, ice crystals begin to form. In colloquial terms this takes on the appearance of ‘slush.’ By this point, the water is already expanding. If contained within a rigid pipe, the pressure within the pipe will rise. If the pressure in the pipe exceeds the physical strength of the pipe, the pipe will deform or even burst. Typically, a pipe will burst at areas of stress concentrations, such as pipe bends or elbows.
In some cases, the rise in pressure may cause the pipe to burst while still in the slush stage, before solid ice forms. This typically results in an immediate leak. At other times, solid ice forms in a portion of the pipe before an adjacent portion fails. In such cases, a small amount of water/slush leaks from the pipe, while the solid ice upstream plugs the pipe and prevents the flow of water. In these instances, it is not until days later when the cold weather passes and the ice within the pipe melts that the leak is apparent.
For this reason, it is advised that if a section of pipe is suspected to have been exposed to freezing temperatures, a thorough inspection of the piping system in the suspected area should be conducted immediately. Discovery of a pipe failure prior to thawing of the ice within a damaged pipe may prevent catastrophic water damage to the building.
What Is the Role of Pipe Insulation?
When reporting after site inspections of freeze damaged pipes, I am often asked whether the pipes were insulated. In many instances, given this question in the context and site
conditions of the loss, it is apparent that the intent and effect of
pipe insulation is not widely understood.
In general, insulation is used to slow the rate that heat transfers from one thing to another. It is also worth noting that heat only travels from high temperature to low temperature. Therefore, it is not a matter of the cold getting into a pipe to freeze it, but rather the heat leaving the pipe.
Pipe insulation is most beneficial when a constant or intermittent flow of temperature conditioned water passes through the pipe. For instance, if building heating system water is flowing through a pipe to deliver water to a heating coil, insulating the pipe would prevent the hot water within the pipe from losing its heat energy to the air surrounding the pipe. However, in the case of a fire sprinkler pipe, there is no flow of water unless there is a fire. There is no source to provide heat energy to the stagnant water within the pipe. If such a pipe is exposed to freezing temperatures, it is only a matter of time before the pipe will freeze, with or without insulation. A similar example is a plumbing supply pipe, wherein the water may be stagnant during overnight hours when restrooms and other fixtures are not in use.
What About Building Insulation?
Building insulation can be vital to protecting pipes from freezing. Of equal importance is the placement of building insulation with respect to piping. Keep in mind that insulation is intended to slow the flow of heat transfer from areas of high temperature to areas of lower temperature. In the case of a building in the winter months, the high temperature exists in the conditioned interior of the building and the lower temperature is outside. To protect pipes from freezing, building insulation should be placed between the piping and the building exterior. If building insulation is placed between the building interior and the piping, the insulation would prevent the building heat from protecting the pipes from freezing.
In many instances, I see buildings with roof insulation and supply plumbing or fire sprinkler piping in the space between the roof insulation and the lay-in ceiling below. The building insulation is appropriately placed with respect to the piping to allow the heat from the building interior to heat the piping. Unfortunately, at some later point in time, insulation was added to the top side of the lay-in ceiling to prevent noise transfer between rooms via the ceiling space. The new insulation was placed between the building interior and the piping, thereby slowing the rate at which heat is transferred from the building interior to the space above the ceiling, increasing the risk of a pipe freeze.
Can Moving Water Freeze?
In the southern states, many say that you should let just a bit of water run from a faucet or two during the nights of a cold spell to prevent the pipes in the crawl space from freezing. Does this really work? The answer is, yes, but not for the reason most people think. A common misconception is that moving water will not freeze. Obvious cases against this notion are frozen rivers or even water falls which commonly occur in extremely cold climates. The reason that running water from a faucet prevents freezing is because the water coming from the pipes below ground is relatively warm. As the water flows through the piping above ground, it begins losing its heat to the surrounding cold air. The pipes will be prevented from freezing as long as the flow of water is fast enough to carry the water through the crawl space and into the house before it loses enough heat to freeze.
Another illustration of this is the failure of a heating coil I inspected in an air-handling unit at a medical facility. The coil piping was such that when there was no call for heat, the control valves would divert heating system water away from the coil. The residual water in the coil would remain stagnant unless cold air temperatures within the air-handling unit triggered the freeze protection controls sequence of operation which activated the coil’s recirculation pump. However, the designer failed to cause the control valve to open to allow heating system water into the coil piping loop. Only the small amount of residual water in the coil and associated branch piping were recirculated through the coil to prevent freezing. Despite the high flow rate of the water through the coil, the water soon cooled to near freezing and the coil burst.
As discussed above, a proper investigation into a pipe freeze failure must consider the pipes as part of the overall building system. Building codes and industry standards should be examined when evaluating piping system installations. Improper system operation can also be a contributing factor to the circumstances that lead to failures. Often, extensive experience and a solid understanding of system fundamentals are the best tools in determining the root cause of pipe freeze failures.