Do hot or cold water pipes freeze first?

Author: Alvis Murazik  |  Last update: Sunday, June 8, 2025

But luminaries including Aristotle, Rene Descartes and Sir Francis Bacon have all observed that hot water may actually cool more quickly. Likewise, plumbers report hot water pipes bursting in subzero weather while cold ones remain intact.

Will hot water lines freeze before cold water lines?

Another interesting thing with freezing water: The water in the hot-water lines freezes faster. This is insanely counterintuitive but true.

Which freezes first, hot water or cold water?

Hot water can in fact freeze faster than cold water for a wide range of experimental conditions. This phenomenon is extremely counterintuitive, and surprising even to most scientists, but it is in fact real.

Which water pipe freezes first?

Pipes that freeze most frequently are: Pipes that are exposed to severe cold, like outdoor hose bibs, swimming pool supply lines, and water sprinkler lines.

Should you leave hot water running to keep pipes from freezing?

It also is recommended to turn on both hot and cold faucets near outside walls to allow a small trickle of water to run during the night and, if not used often, during extremely cold days as well.

Why do hot water pipes freeze first?

Will running hot water unfreeze cold water pipes?

If your cold water has frozen but water comes out of your hot water pipe, let the hot water run for 20 minutes. Sometimes this can help to thaw a frozen cold water pipe. If that doesn't work or your hot water pipe is frozen, use a hair dryer set on high heat.

Do you drip faucets during a freeze?

Should You Drip Faucets In Cold Weather? Yes, according to the Red Cross, the short answer to that question is you should.

Can one pipe freeze and not the other?

Check all faucets in your home to find out if you have frozen pipes, if one pipe freezes, others may too. Check around the home for areas where water supply lines are located in unheated areas.

Do you run hot or cold water when it freezes?

Cold Weather Precautions
  1. It's important to remember that both hot and cold water pipes may freeze. ...
  2. Let the water run — Leaving a small but steady stream of lukewarm water running will keep the water moving through the pipes.

How do I know if my hot water pipe is frozen?

No water or a slow trickle when a faucet is used. Whistling and banging coming from pipes, or strange bubbling sounds when you flush a toilet. Dampness, puddles, or rings on drywall or ceilings—signs of an urgent issue.

At what temperature does hot water freeze instantly?

Water would have to be -42 F to immediately freeze. What is happening instead is that the hot water is quickly condensing into water droplets, essentially turning into steam. This happens at around -14 F and below and is much more possible in some of the colder U.S. states.

Where does water freeze first?

The reason water freezes from the top down is because, unlike almost everything else, water gets less dense when it freezes.

Does water contract before it freezes?

When liquid water is cooled, it contracts like one would expect until a temperature of approximately 4 degrees Celsius is reached. After that, it expands slightly until it reaches the freezing point, and then when it freezes it expands by approximately 9%.

Why is my hot water not working but cold is?

Possible Issue: One of the most common culprits for this predicament is a malfunctioning differential valve. This valve is responsible for controlling the flow of hot and cold water in your plumbing system. When it's not functioning correctly, it can lead to an imbalanced water supply, leaving you with cold water only.

How long does it take for water pipes to freeze?

With this in mind, expect most pipes to freeze within six to eight hours. Uninsulated exterior pipes can freeze in under six hours if the temperature is below 20 degrees. It takes at least 12 hours for unprotected pipes to freeze at 32 degrees.

Why does hot water freeze faster?

The reason for the observation is warm water evaporates quickly than cold water. As evaporation will produce the cooling effect water will get cooling immediately and freeze earlier than cold water.

Which pipes freeze first, hot or cold water?

Mpemba and Osborne's 1969 paper in Physics Education presented evidence that hot water freezes faster than cold water.

Is it bad to run hot water on frozen pipes?

Pipe-thawing options: There are several things you can do to thaw your home's pipes. Here's a list: Probably the most popular and safest pipe-thawing option is to use hot water. Wrap and secure heavy towel or burlap bag around pipe to concentrate and hold heat against it.

Can pipes freeze in one night?

Yes, pipes can freeze overnight if temperatures plummet drastically. Uninsulated pipes in unheated areas like attics or exterior walls are most vulnerable.

Will shutting off water keep pipes from freezing?

Prevent Frozen Pipes

Moving water keeps pipes from freezing. Find shut off valves for emergencies. Insulate pipes in unheated areas. Open cupboards and vanities to warm pipes.

How many faucets to drip in freeze?

In general, you should let at least one faucet drip in each section of your home. This is particularly crucial if your home has multiple floors or distinct areas, like an extension or a wing. If you have the option, choose faucets that allow you to control hot and cold water separately and let both drip slightly.

Can house pipes freeze without bursting?

Even if a pipe does not burst, the expanding ice can still cause damage. This can lead to leaks which can cause significant damage over time if they go unnoticed. The best way to protect against frozen pipes and the resulting water damage is with an automatic water shut-off device.

What not to do when your water pipes freeze?

Don't ever try to thaw pipes with a:
  1. Blowtorch.
  2. Gas heater.
  3. Kerosene heater.
  4. Propane heater.
  5. Other open flame appliances.
  6. Any device near insulation.
  7. Electric device with extension cord.
  8. Electric heater, blow dryer, or other device near water.

Is it better to cover outside faucets or let them drip?

If you live in a climate with freezing temperatures, you'll want to cover your outdoor faucets in the winter rather than dripping them. Even with a vigorous drip, frigid temperatures can travel through your faucet and freeze the connecting pipes. Before using a cover, you'll need to properly winterize your faucet.

How do people up north keep their pipes from freezing?

Generally, houses in northern climates are built with the water pipes located on the inside of the building insulation, which protects the pipes from subfreezing weather.

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