What do you do if your hot water pipe is frozen but not cold?

Author: scraper  |  Last update: Sunday, September 27, 2026

If your hot water pipe is frozen but the cold water still flows, leave the hot water tap slightly open. Trace the hot water line back from the faucet to find the freeze—often near an exterior wall or uninsulated space—and carefully apply heat using a hair dryer, space heater, or hot towels.

How do I unfreeze my hot water line?

Open a Hot Water Valve

By opening faucets, water will have a path to flow as the pipe unfreezes. Steam will also need a place to go as heat is applied. As the pipe thaws, running water will accelerate the defrosting process. Therefore, it's beneficial to have faucets running until the pipe is completely thawed.

Can just your hot water pipes freeze?

Yes, hot water pipes can freeze just as easily as cold water pipes. In fact, because they sit idle when not in use and contain less dissolved air, they can freeze even faster than cold pipes. Once frozen, the expanding ice can cause severe cracks or bursts, resulting in costly water damage.

Do frozen pipes eventually thaw out?

Your pipes will eventually begin to thaw on their own once the temperatures rise above freezing. As they do so, you may begin to hear your pipes making gurgling, clanging, or banging sounds as the ice begins to move. The hot water heater may do the same.

What is the fastest way to unfreeze water pipes?

To thaw frozen pipes quickly, immediately open your faucets and safely apply heat to the frozen section—working from the faucet toward the blockage. Use a hair dryer, an electric heating pad, or towels soaked in hot water. Never use an open flame or blowtorch, as this poses a severe fire hazard.

How To Fix Hot Water Pipe That's Frozen But Not Cold (What To Do If A Hot Water Pipe Is Frozen?)

Should I leave faucets on if pipes are frozen?

The combined pressure of the expanding and shrinking ice blockage and the increasing water pressure behind it can cause pipes to leak or burst. This is why you'll always want to leave a faucet on if a pipe is frozen completely, even if there's not enough water flow for a drip.

How much will a plumber charge to unfreeze pipes?

If a pipe is frozen but not damaged, a plumber may only need to thaw it. Thawing services typically cost $100 to $200 when pipes are easy to access. When pipes crack or burst, repairs become more complex and expensive.

Is 4 hours long enough for pipes to freeze?

On average, pipes can freeze within six to eight hours when temperatures stay at 20 degrees or lower. If pipes are poorly insulated or exposed to drafts, they may freeze even faster. This is why pipes often freeze overnight when temperatures drop significantly.

What do plumbers use to thaw pipes?

A thaw machine is a portable device that plumbers use to thaw pipes quickly.

How many faucets should you drip during a freeze?

The general rule is to allow one faucet to drip. It should be the one farthest from where water enters your home. This strategy will make sure that water moves through the entire plumbing system. Thus, it will reduce the risk of freezing.

What not to do when pipes are frozen?

Do not use a blowtorch, kerosene or propane heater, charcoal stove, or other open flame device.

Where do hot water pipes freeze first?

As temps drop, the risk of having frozen pipes in your home increases. Typical high-risk areas for freezing include pipes within exterior walls, as well as exposed pipes that run through unheated or uninsulated areas such as attics or basements.

What if the cold water pipe is frozen but not hot?

Turn on both hot and cold water faucets connected to the frozen pipe. This relieves pressure in the system and allows water to flow once thawing begins. If only cold water is frozen but hot water works, let the hot water run for about 20 minutes, as this might help thaw the frozen cold water pipe.

What happens if your hot water pipes freeze?

Frozen pipes are likely to burst, leading to severe water damage in homes and businesses. Pipes in unheated or uninsulated areas like attics, basements, and garages are most vulnerable to freezing.

Should I call a plumber to unfreeze pipes?

Trying to fix frozen pipes yourself works only if the pipe is exposed, hasn't burst, and you have the right tools. But in many cases, calling a licensed plumber is the safest option.

Can a hair dryer thaw frozen pipes?

If your pipes are frozen, a hairdryer is the safest way to thaw it, the IFD says. Using a flame or torch is not recommended. “Homeowners who experience a frozen pipe can try to thaw the line safely by using a hair dryer.

How long does it take for a plumber to unfreeze pipes?

With professional thawing equipment, plumbers can thaw a frozen pipe in minutes. A hair dryer or space heater may thaw a pipe in as little as 30 minutes, but it could take much longer depending on the length and location of the pipe.

Does homeowners insurance cover frozen pipes?

Yes, homeowners insurance typically covers water damage caused by burst frozen pipes, provided the incident was "sudden and accidental" and you took reasonable precautions to prevent it.

Should you leave faucets on if pipes are frozen?

Letting the Water Run

Rather, opening a faucet will provide relief from the excessive pressure that builds between the faucet and the ice blockage when freezing occurs. If there is no excessive water pressure, there is no burst pipe, even if the water inside the pipe freezes.

Can water freeze in 30 minutes?

Yes, water can freeze in 30 minutes, but it typically requires small volumes or specialized techniques. In a standard home freezer, common items like ice cubes or water bottles usually take much longer—between 2 to 4 hours—to freeze completely.

Will pipes freeze in a house without heat?

Yes, pipes will freeze if the heat is off and the outside temperature drops below freezing. Without active heating, a home's interior temperature generally drops to freezing levels within 6 to 8 hours, placing your pipes at severe risk of cracking and bursting.

What is the 135 rule in plumbing?

In plumbing, the "135-degree rule" is a code standard that dictates how much a horizontal drain pipe can bend or change direction. It limits the total cumulative angle of pipe fittings before a system requires an access point (cleanout) or must be vented, ensuring proper flow and preventing chronic clogs.

How much does Roto-Rooter charge to unfreeze pipes?

Roto-Rooter costs $100 to $600 on average for minor fixture repairs or clogged plumbing. Roto-Rooter rates for fixing a toilet or sink are less than for unclogging drains and sewer lines. Plumbing services for emergencies like burst pipes cost $1,000 to $3,500.

Do plumbers charge a call-out fee?

Yes, most plumbers do charge a call-out (or service) fee. This typically costs between $50 and $150 and covers the plumber’s travel time, fuel, and the initial labor required to diagnose your plumbing issue.

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