How a Frozen Pipe Bursts | Ask This Old House

Summary

Frozen pipes are a common issue in cold climates, and sudden temperature drops can cause severe damage. As water freezes and expands by 9%, the real danger lies in the immense pressure built up, potentially reaching 25,000 psi. This pressure can cause pipes and radiators to burst. To prevent such disasters, it’s essential to know where the main water shut-off valve is, insulate exposed pipes, and allow faucets to drip to relieve pressure. Additionally, opening cabinets or providing heat can help keep pipes warm during extreme cold. Following these simple precautions can help avoid costly water damage in your home.

Takeaways

• 😀 Cold weather can lead to frozen pipes, causing water damage and potentially dangerous bursts.
• 😀 Water expands by 9% when it freezes, but it's the pressure buildup downstream that causes pipes to burst.
• 😀 When water freezes in pipes, the pressure can rise as high as 25,000 psi, which is enough to cause significant damage.
• 😀 A demonstration showed how a frozen pipe with increasing pressure can quickly exceed the gauge limits in seconds.
• 😀 The importance of a main water shutoff valve is crucial during a pipe burst to minimize water damage.
• 😀 It's essential to know the location of your shutoff valve and to understand how to use it quickly in case of emergencies.
• 😀 To prevent frozen pipes, insulating exposed pipes can help, especially in cold climates or areas hard to access.
• 😀 One simple preventive measure is to open kitchen cabinet doors to allow warmer air to circulate around pipes.
• 😀 If a pipe is about to freeze, relieving pressure by cracking open a faucet can prevent dangerous pressure buildup.
• 😀 During extreme cold, letting faucets drip—especially the farthest ones from the water supply—can help prevent pipes from freezing.

Q & A

What causes pipes to burst when water freezes inside them?

When water freezes inside a pipe, it expands by about 9%. This expansion increases the pressure within the pipe, which can build up to as much as 25,000 psi, causing the pipe to burst.

Why isn’t the expansion of water enough on its own to burst most pipes?

While water expands by about 9% when it freezes, this is typically not enough to cause a burst. The real danger comes from the pressure buildup downstream of the frozen section of pipe.

How high can the pressure in a frozen pipe go?

The pressure inside a frozen pipe can escalate to as high as 25,000 psi, which is what causes the pipe to rupture, not just the 9% expansion of the water.

What’s the primary reason a burst pipe causes so much damage?

The damage from a burst pipe is caused by the massive pressure buildup within the pipe, which can force water to flood the area quickly, leading to severe water damage in the home.

What should you do to prevent frozen pipes in cold weather?

To prevent frozen pipes, you should insulate exposed pipes, keep cabinet doors open to allow heat circulation, and let faucets drip to relieve pressure. You should also know where your main water shut-off valve is located in case of an emergency.

How can you relieve pressure in a frozen pipe before it bursts?

You can relieve pressure by slightly opening a faucet located far from the frozen pipe. This allows water to escape slowly, reducing the pressure buildup that could lead to a burst.

What is the importance of knowing where your main water shut-off valve is located?

Knowing where your main water shut-off valve is located allows you to quickly stop the water supply in case of a frozen pipe or burst pipe, minimizing water damage to your home.

What is a common situation where pipes are likely to freeze in a house?

Pipes located in exterior walls, such as those behind kitchen cabinets or under sinks near windows, are particularly vulnerable to freezing because they are exposed to colder temperatures from outside.

What type of insulation is commonly used to protect pipes from freezing?

Common insulation for pipes is foam pipe insulation, which often comes in split pieces that can be easily applied over exposed pipes to protect them from freezing.

How can you protect your kitchen sink pipes from freezing?

One simple method is to open the cabinet doors under the sink to allow warm air from the rest of the house to circulate around the pipes and prevent them from freezing.