I am a renter with water pipes that are inaccessible at some points, and which may freeze in the winter. I am doing my best to prevent this, including heating my apartment, trickling my faucets, and potentially doing some more insulation or electric heating.

If my pipes freeze and I try to thaw them out by using hairdryer or other similar heat source to apply heat to a single point along the pipe, can you give me any rules of thumb for how long of an ice block I could reasonably expect to melt? This probably varies based on various factors (like maybe the pipe material/dimensions, the temperature, the heat source, etc), and I would be interested in a range of conditions.

For specificity, you can imagine that the pipes are copper, the temperature drops to 10 deg F (-12 deg C) area and remains there for 12 hours after the freeze, and I use an 1800-watt hairdryer.

  • 1
    Have they ever frozen before? Pipes freezing in occupied living quarters is rare.
    – JACK
    Sep 27, 2020 at 23:48
  • @JACK Thanks! They have frozen before, but that was before I started trickling my faucets in the winter. This is more of a precaution. I'm not sure where the freeze occurs but I think it is in a two-storey vertical pipe passing up from a partially heated cellar through a difficult-to-access exterior wall. Not sure about the degree of insulation.
    – capet
    Sep 27, 2020 at 23:56
  • 1
    a fan would help keep the pipes the same temp as the room, without fire hazards.
    – dandavis
    Sep 28, 2020 at 21:51
  • 1
    Well a fan increases heat sink performance by larger factors, maybe 10X for something indirect like that. Putting in 10x more heat means it will freeze 10X further away.
    – dandavis
    Sep 28, 2020 at 21:59
  • 1
    you can test effectivness of different measures and generally as a warning by monitoring the temp of the water you're bleeding; if it's under a few C, look out.
    – dandavis
    Sep 28, 2020 at 22:01

1 Answer 1


Your best bet is to prevent the pipe from freezing in the first place. Once the pipes are frozen, a hair dryer will heat up a copper pipe slightly and that heat will travel down the pipe melting the outside of the ice column and breaking it free and it will travel down the pipe. To melt it completely would take hours. A propane torch would do it much faster but they could be a fire hazard waving it around and then there's a chance of ruining a solder joint.

There are pipe heaters especially designed for preventing pipe from freezing. You wrap them around a pipe, plug them into a wall outlet and set the thermostat to the desired temp. They come in different lengths and operate on about 5 watts per foot. See the picture below.

enter image description here

This one is from LingRan Industries, which I have no interest in.

  • Thanks @JACK! How well would you expect this to work for an application where I have about 30 feet of pipe between the nearest two accessible points? (I think that 30 foot span is where the freeze occurs).
    – capet
    Sep 28, 2020 at 1:49
  • 1
    It would probably be effective if you wrapped the pipe as much as possible at the two accessible locations and set the thermostat higher.
    – JACK
    Sep 28, 2020 at 2:03
  • Thanks! That makes sense.
    – capet
    Sep 28, 2020 at 2:15
  • I will mark this as the answer tomorrow.
    – capet
    Sep 28, 2020 at 3:37
  • 1
    If you have 30 feet of pipe exposed to the freezing elements, you probably need to move that line.
    – mark f
    Sep 28, 2020 at 20:45

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