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Make Sure Your New High-Efficiency Furnace Condensate Pipe Won't Freeze Up

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All types of furnaces have drain pipes, or condensate pipes. These pipes direct condensation that collects during the heating process out of the heater, and usually outdoors. In the Northern United States, it's important to make sure the condensate pipe won't freeze up during winter when you're installing a new furnace -- especially if you're installing a high-efficiency furnace, as these models produce more condensation than regular furnaces.

High-Efficiency Furnaces Produce Lots of Condensation

High-efficiency furnaces produce lots of condensation, because condensation is created during the heating process and high-efficiency furnaces are extremely good at heating. In furnaces, heat is transferred from an exhaust product to the air (which is then directed to rooms). As the exhaust product cools, it produces condensation. High-efficiency furnaces extract as much heat from their exhaust products as possible, so the exhaust products in high-efficiency furnaces produce lots of condensation. says a high-efficiency furnace can produce as much as 5 or 6 gallons of water from condensation each day.

Condensate Pipes May Freeze Up in the Winter

Most of the time, condensate pipes are set up to carry condensation outdoors through a hole in an exterior wall. The water is able to drain harmlessly into the ground.

This system is fine for most of the year, but condensate pipes can freeze up in the winter. Ice builds up when the water in a pipe freezes faster than it drains. Once ice starts forming, it will continue to form until temperatures go above freezing and the pipe can thaw. Eventually, the pipe may freeze shut if the weather remains cold, as it does for long periods of time in much of the Northern U.S.

The issue is compounded in extremely cold weather. Water will freeze quickly when temperatures are well below freezing, but this is also when you'll most need your furnace. Running your furnace will generate more condensation, which will create more water that can freeze.

If your condensate pipe freezes and temperatures don't warm up, you'll need to thaw the pipe out yourself. This is an easy do-it-yourself project, but it is a hassle nonetheless. A condensate pipe can be thawed by:

  • wrapping warm towels around the pipe
  • pouring hot water over the pipe
  • securing heat tape to the pipe

Condensate Pipes Can Be Installed to Reduce Freezing

When installing a new furnace, a new condensate pipe can be installed so that the risk of freezing up is reduced. There are a few ways your furnace installation technician might set up the pipe so it's less likely to freeze. To accommodate the increased amount of condensation that a new high-efficiency furnace will produce, your technician can do the following:

  • install a vertical pipe, instead of a horizontal one, so water drains faster
  • install an oversized pipe so ice is less likely to block the entire pipe
  • insulate the pipe so ice won't build up

Prevent Your New High-Efficiency Furnace's Pipe from Freezing

Many times, new furnaces are installed using existing condensation pipes because pipes rarely wear out. If you're having a high-efficiency furnace installed, though, your current furnace's drain pipe might freeze up during the winter once you connect a model that produces more condensation. You may need a new pipe.

So you don't have to go out in the cold and thaw your furnace's drain pipe, talk with a heating installation technician, such as those at Glendale Heating & Air Conditioning, about ways they can set up the pipe so that the risk of ice building up is reduced. Installing a vertical pipe, and oversized pipe or insulation around a pipe is easy when installing a high-efficiency furnace, and taking such a preventative step will keep you inside where it's warm during the winter.