Internal Roof drain freezing


Old 02-12-14, 10:59 AM
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 3
Internal Roof drain freezing

We have a flat roof with a very slight pitch. There is a 5 inch PVC pipe running through our attic and out the soffit of a Mansard roof. With the cold and all the snow we have been having, the water freezes at the outlet at the soffit. We actually broke off the drain pipe to the ground and the water started flowing. But now it formed a giant icicle to the ground and again it froze up and backed up causing leaking in the attic and into my bathroom below. We purchased a heat wrap wire, but the instructions said it could not be used on plastic pipes if they do not have water in them at all times. This pipe obviously does not. Any suggestions as to what we can do? Thank you. Tired of putting hair dryer and heating pad on the pipe every night.
Sponsored Links
Old 02-12-14, 05:44 PM
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 3
I see I didn't explain myself clearly. The 5 inch pipe is an internal drain pipe from the roof to the eave in the attic. The pipe goes through the eave and outside into an oversized down spout. (As I said before, the down spout is no longer there and will be reattached when the weather permits.) The roof itself is not leaking. Nor is the pipe. The water is coming into the attic where the pipe is connected to the drain from the roof with a rubber connector.
Old 02-12-14, 06:33 PM
Join Date: Oct 2008
Location: New England
Posts: 10,311
Likes Received: 12
I don't really have a good answer, but to let you know I looked here is what little experience I have with drains from a flat roof. In my cold climate I have seen some that drain down through heated spaces. That obviously prevents the freeze issue. As for any water source dripping out into freezing air, it will ice up quickly.

If you can get the flow of water directed into a continuous drain that is sheltered or insulated from the cold then maybe it will drain without freezing. There are many varieties of heat tapes, think farm supplies or Graingers.

Old 02-12-14, 06:51 PM
Tolyn Ironhand's Avatar
Group Moderator
Join Date: Nov 2007
Location: Twin Cities, MN
Posts: 12,715
Likes Received: 14
Heat tape is your answer. Here is one example: PSR Heating Cables Look at gutter heat tape, not heat tape for water lines.
Old 02-13-14, 06:27 AM
Forum Topic Moderator
Join Date: Sep 2005
Location: USA
Posts: 4,507
Likes Received: 6
I think Tolyn got it. Gutter heat tapes can be run inside the pipe to keep them clear.

My only concern would be if they can be safely used in a pipe that runs inside the house. I've never used them before, so I can't say whether they are approved for this kind of usage and if there would be any significant safety concern with running them in a pipe that runs inside your structure.
Old 02-13-14, 09:27 AM
Thread Starter
Join Date: Feb 2014
Location: USA
Posts: 3
Thanks for your suggestions. I've looked into various gutter heat wraps/tapes. However, I'm getting very confused. Some seem to have to be attached to the outside of the downspout and then insulated and protected (Sounds odd for a downspout). Other say you can place them down the downspout itself which of course means it would be exposed to water. Has anyone actually used these in a similar application. We have a mansard roof which is why our roof is flat.
Again, Thank you,

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Thread Tools
Search this Thread
Display Modes