At What Temperature do Pipes Freeze?


Frozen pipes are a major issue facing homeowners of all stripes, and every year they lead to expensive repairs from pipes bursting leading to flooded basements, bathrooms, and more. This leads to the logical next question which is – at what temperature do pipes freeze?

The answer to this question might seem simple, but because houses have differing degrees of insulation, the external temperature needed to freeze pipes varies from one house to another.

Speaking generally though, pipes will freeze when the outside temperature reaches 20°F for six consecutive hours. This will also vary somewhat based on geography, as houses in northern climates tend to be better insulated and will take longer for their pipes to freeze than houses in southern climates.

Let’s take a closer look at what temperature is needed to freeze pipes, and what to do to prevent damage from pipes freezing inside your home.

What Temperature Causes Pipes to Freeze?

As you probably know, water freezes at 32°F. However, that doesn’t mean the water in your home’s pipes will freeze at that exact temperature. Interior pipes are protected by the insulation and heating of your home, so you don’t need to start worrying every time the temperature dips below zero.

It’s not until temperatures reach 20°F that you need to worry about pipes inside your home freezing. Of course, water doesn’t freeze instantaneously, so it generally takes about 6 hours of sustained below 20°F for pipes to fully freeze.

This is a general rule of thumb though, and there are multiple factors that influence the time it takes for a house’s pipes to freeze.

The first major factor is insulation. Heavily insulated houses are able to withstand lower temperatures and longer cold periods before their pipes freeze over.

As you might expect, houses in northern regions are designed and built with better insulation – so they can withstand a cold snap better than houses located in warmer southern regions.

The next factor is the location of the pipes within your home. As you might expect, pipes located in the less insulated areas near the house’s exterior are more prone to freezing than pipes located in well-insulated central areas.

This is especially true of your house’s exterior water faucet (also called a hose bib). This section of plumbing isn’t protected by heat and insulation like your home’s interior pipes, so it’s subject to freezing when the temperature drops below freezing for any significant period of time. You’ll need to turn off your home’s outside water supply to prevent the exterior faucet pipes from freezing over.

How to Prevent Pipes from Freezing?

When pipes freeze over the main cause for concern is bursting. Burst pipes lead to leaks, flooding, and extensive plumbing repairs, so you want to do everything possible to prevent pipes from freezing and bursting.

So how do you prevent your house’s pipes from freezing?

Heating

The main thing you can do to prevent pipes from freezing is keeping all areas of your house well heated. You don’t want any area with water lines to fall below 32°F for any sustained length of time.

If you’re going to be away from your home for a significant period of time, leave the heat on a minimum of 55°F. You might be tempted to set the heat lower to save on heating costs, but the temperature is unpredictable and you don’t want to be subject to a sudden cold snap freezing your pipes.

Leave Water Running

You might not think this would be helpful, but leaving one or two water faucets running at a slow dribble will keep water moving through your pipes so it can’t collect and freeze.

sink with water running
A small amount of running water will help keep pipes from freezing over. [Source]

Apply Heating Cable

If you want to heat a section of pipe and prevent it from freezing, then there are purpose-built pipe heating cables you can install yourself. All you need to is wrap the heating cable around your plastic or metal pipes, and plug the cable into the wall.

A built-in thermostat controls the heating cable, so it will only kick in when temperatures fall below a certain threshold. Check out the HEATIT HISD 60-feet Pipe Heating Cable for a well-made heating cable.

Seal Gaps in Insulation

Pipes freezing are typically a problem in old houses with mediocre insulation and drafty windows and doors. If that sounds like your house, then an easy way to improve your insulation is by sealing any leaks allowing cold air to flow into your home.

Examine any gaps around, windows, door frames, vents, and electrical wiring. If you find air leaks, apply caulking or insulation to seal off the gap and prevent any cold air from flowing in.

Open Kitchen & Bathroom Cabinets

Kitchen and bathroom faucets are often built facing an exterior wall, leaving them subject to freezing over in cold snaps. Leaving the cabinets open will allow warm air to circulate through the pipes and help prevent freezing.

kitchen cabinet open
Leaving cabinet doors open will allow warm air to flow and prevent pipes from freezing. [Source]

Turn off Outside Water Supply before Winter

The most vulnerable pipes in your home are the pipes leading to the exterior water faucet (the hose bib). Because they direct water to an outdoor faucet, they aren’t subject to the same level of insulation as your interior pipes.

You’ll want to turn off the water supply to these pipes before winter hits to prevent the water inside them from freezing and bursting. If you have a hose attached to your hose bib, then you’ll also want to remove it and drain any water out of it before storing it away for the winter.

Keep Garage Doors Closed 

Make sure to keep your garage doors closed in cold weather, especially if there are any water supply lines running through your garage.


Denis Gardner

I've loved tinkering and fixing things for as long as I can remember. So, naturally, I gravitated towards DIY and home improvement when I bought my first home. Nowadays you can find me writing about my passions or messing around with my newest tool!

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