All residential furnaces have condensate pipes through which water that collects in them drains out. In most cases, the pipes direct the water outdoors through an exterior wall. If you live in the Northern United States and are replacing your furnace during winter, make sure that the cold weather won't make your new furnace condensate pipe freeze up -- especially if you're upgrading an older furnace to a high-efficiency model.

High-Efficiency Furnaces Create Great Amounts of Condensation

High-efficiency residential furnaces produce a lot of condensation. During the heating process, heat is transferred from an exhaust product to air, which is directed into the home. The cooling of the exhaust product produces condensation. The more efficient the process is, the more the exhaust product is cooled -- which produces more condensation. Some high-efficiency models are so efficient that they'll produce 5 to 6 gallons of condensation in a day.

Condensate Pipes Can Freeze in Cold Weather

When the weather's above freezing, condensation drains out of the condensate pipe without an issue. When temperatures drop below 32°F, though, water can collect and freeze in the pipe. Once ice begins forming in the pipe, it will continue to until the weather warms and thaws the pipe.

In the Northern U.S., temperatures often remain well below freezing for extended periods of time, and condensate pipes can completely freeze up. Once a pipe freezes closed so that water can't drain out, a furnace will quickly become backed up with condensation and soon stop working.

The problem is compounded by extremely cold weather. When temperatures are in the single digits or below 0°F, the water in a condensation pipe will begin to freeze particularly quickly. This is also when a furnace is most needed, though, so it's impossible to not produce condensation.

You Can Thaw Frozen Condensate Pipes

If your condensate pipe freezes closed, there are a few ways to thaw it out without waiting for the weather to warm up. You might try the following:

• wrap the pipe in warm towels
• pour warm water over the pipe
• put heating tape on the pipe

While these techniques will work, they shouldn't be used as a permanent solution. After all, you can't do any of these if you aren't home.

Technicians Can Install Condensate Pipes to Reduce Freezing

A better solution is to install a condensate pipe so that the risk of freezing is reduced. There are several ways to minimize the likelihood of condensation freezing in the pipe:

• install a new condensate pipe that's vertical, rather than horizontal, so water drains quickly
• put in an oversized condensate pipe, so ice is less likely to completely block the pipe
• insulate the condensate pipe to keep the water in it warmer

Often, technicians will simply use the current condensate pipe when installing a new residential furnace. When switching from an old furnace that wasn't terribly efficient to a new, high-efficiency model that could produce up to 6 gallons of water, however, you should have a new condensate pipe installed. Putting in a vertical, oversized or insulated pipe won't be too difficult for your technician, and it will help ensure your furnace works well in cold weather.

If you're having a new high-efficiency furnace installed, don't just focus on the residential furnace replacement itself. Also take some time to discuss the condensate pipe and how to prevent it from freezing up in the winter. When temperatures remain below freezing for an extended period of time, which they'll do in the Northern U.S. during winter, you'll be glad you had a new condensate pipe installed when you replaced your furnace.