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Old 01-29-2009, 08:12 AM   #16
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Frozen Vent Pipe


If you read the label on the heat tape, it states to be used for water filled pipes only.

As stated earlier ideal attic temperature is as close to the outside ambient temp as possible. Having it warmer will cause condensation which in itself brings a whole new set of problems much worse than frozen pipes.

Insulating the pipe itself would be OK.

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Old 01-29-2009, 08:34 PM   #17
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Hi Brokenknee, hope your knee is better. I agree that if the attic is not insulated properly condinsation will damage the whole roof structure and work its way down the walls totally destroying them. I guess I should have included pictures. Anyway so insulating just the pipe will possibly stop the vent from freezing?

I am loving these forums because with each reply brings up different thoughts.

So lets say the vent pipe is not insulated since that is the normal installation and the pitch is proper. Any moisture making its way up the vent will collect on the interior pipe walls and pool enough to become heavy and drip down the pipe. If it is cold enough in the attic the moisture can freeze within the pipe in the attic and not necessarly where the pipe goes through the roof. Then as more moisture makes its way up the vent it can compound onto what is already frozen and eventually clog the pipe. WOW, that is some chunk of ice lol.

So insulating just the pipe will stop keep the vent pipe warm enough especially with the open end exposed to the atmosphere?

I am thinking that to totally prevent the vent pipe from freezing the area around the vent pipe needs to stay above 32 degrees F. This can be accomplished by installing some kind of attic insulation that allows proper venting for the roof?

As I continue on my rant, I think I will explain this to death, lol.

Thanks Brokenknee!.
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Old 01-29-2009, 08:56 PM   #18
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Frozen Vent Pipe


The knee is pretty good, will most likely always have some discomfort. I have been back to work since the beginning of November.

Insulating the pipe may work, it will help keep the interior of the pipe above freezing. That would be my first attempt to solve the problem.
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Old 01-29-2009, 08:59 PM   #19
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Frozen Vent Pipe


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Originally Posted by joebart View Post
You seem to missunderstand what I typed. Please read it again before continuing. Do not allow the vent pipe to vent into the attic. It MUST exit the roof and be at least 18" above the roof surface OUTSIDE of the house!

Using heat tape on PVC pipe will burn down your house in a matter of time.

Insulating the roof rafters with a foil insulation will keep the attic at a warmer temp than the outside during the winter time and cooler in the summer. The heat within the attic will keep the vent pipe warm enough to possibly stop it from freezing during those cold months.

So when you climb onto your roof full of ice with a bucket of warm water and make your way across the slippery roof you don't think how dangerouse that is? You don't think of your family's wellbeing if you were to fall and kill yourself? How about when you finally make it to the pipe and I bet you stick you nose right into that pipe to look deep into it to see where the ice has bulit up. So you see the ice and then finaly pour warm water into the pipe and as you pour the water your nose is still over the pipe and once the ice melts you inhale that huge slug of methane gas as well as other sutff that has been collecting their for days.

Don't you think its better and safer to fix a potential problem once the cause is known? Seems like your looking for your 15 minutes of fame. If you continue this method of going up on the roof I am sure to see the OSHA video of your dead body on the ground with a caption saying "Frozen Vent Pipe Got Him"

Please be safe.
Hahaha wow. Yes, as a matter of fact I love to take nice big breaths of methane prior to jumping off my slippery roof. I wasn't responding to anything you said, just the thread in general.
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Old 01-30-2009, 06:34 AM   #20
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Sorry Reilley, I tend to get on the ever popular high horse and spew out all kinds of stuff, lol! thanks for putting up with me.
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Old 02-27-2009, 01:10 PM   #21
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I have a similar problm as you are descriping right now. My 2nd floor ceiling developed a water stain and when I went into the attic I had condensation build-up underneathe where the vent pipes exits the roof. I went onto the roof and the entire vent pipe was frozen. This is a double wall vent pipe that is fed by the furnance and two water heaters. Can I insulate the inside vent in the attic to help prevent this. We have had cold temperatures in Missouri but no snow at all this year, so it is mainly freezing as it comes out of the pipe. One roofer told me to replace the vent stack at the roof since he thought it was defective possibly and forcing the air onto the roof which is causing it to freeze.
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Old 03-14-2012, 01:25 AM   #22
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Frozen Vent Pipe


I have an unusual solution to the "Frozen Vent Pipe" problem that I wish I could say was my own but, I think I saw it years ago on some home improvement show and thought I'd never have a use for it. The problem starts with a 3 story plumbing chase 12inches by 12inches that includes a 3/4inch copper water supply through the bottom 2 stories and a 3inch pvc vent stack that runs up all 3 stories and to about 30inches above the shingles. Since the vent stack is simply a 3inch pipe that ends above the roof; it allows cold air to drop down the pipe creating a 3inch diameter column of freezing cold air through the plumbing chase. This in turn cools the air in the chase and the bottom of the water line freezes forcing me to cut through the sheetrock and hook up welding cables to thaw it.
The solution as I see it is to add two 3inch street elbows to the top of the vent stack and a 12inch length of 3inch pvc with a strainer to prevent any birds, squirrels or other creatures from entering. What you end up with is a candy cane shaped vent that creates an air lock to prevent cold air from entering; since cold air can't rise, it's unable to go up the short side and over the hump to enter the stack, and the fairly stagnant air on the long stack side stays above freezing from the heat transfer through the walls and allows a constant slow rise of warm air to flow up the pipe tending to push the cold air out.
This problem happened in January and I've been letting the faucet trickle to prevent anymore problems this year since running water won't freeze and I'm 59 and not about to roof climb in the cold. I'm wondering if anyone has ever heard of this method and could give me some verification. I can't believe I dreamt it in my sleep but, really can't remember where I saw it. Thought I would glue all the joints and if for some reason a problem developed the added pipe could be cut off.
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Old 11-26-2012, 07:44 PM   #23
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Frozen Vent Pipe


Any further intel on this? I just posted under the above thread in the Introductions section and then did a search and found this thread. My vent is freezing up DAILY now and driving me crazy. Has the person who started this found a solution that works?
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Old 11-27-2012, 11:19 AM   #24
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Ratchye are you still listening? I live in Alaska also and if I could get verification from you that your solution is still working it would greatly ease my mind...Mine is freezing up at -10 and we can get to -60.
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Old 11-27-2012, 11:31 AM   #25
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Company called Heatline makes an "ArcticVent" product. No idea if it's any good, though. And you'd need a place to plug it in.
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Old 11-29-2012, 11:17 AM   #26
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Frozen Vent Pipe


Arctic Vent looks great, and a bout a grand to have one installed. But thanks for the tip.

I took everything I heard and did this: It is old double-walled metal pipe with 3 3/4 " ID; I took an 18" piece of 3" PVC and attached a wide "T". Bought a 12' length of Raychem 7W/foot heat tape and made three loops with it and squeezed them up the pipe and almost out one side of the "T" so I had basically 6 loosely flopping lengths of heat tape inside from end-to-end, slid it down the vent with the "T" perpendicular to prevailing wind to enhance a vacuum effect, and plugged it in. So far it works great, no stink and two gentle plumes of steam rising into the -20 F. night sky...

I took everything I heard and did this: It is old double-walled metal pipe with 3 3/4 " ID; I took an 18" piece of 3" PVC and attached a wide "T". Bought a 12' length of Raychem 7W/foot heat tape and made three loops with it and squeezed them up the pipe and almost out one side of the "T" so I had basically 6 loosely flopping lengths of heat tape inside from end-to-end, slid it down the vent with the "T" perpendicular to prevailing wind to enhance a vacuum effect, and plugged it in. So far it works great, no stink and two gentle plumes of steam rising into the -20 F. night sky...
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Old 11-29-2012, 11:56 AM   #27
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Are you sure heat tape in direct contact with PVC is a good idea?
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Old 11-29-2012, 02:20 PM   #28
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Frozen Vent Pipe


7W/foot heat tape is a newer kind of heat tape product that carries no risk of setting PVC on fire. If that turns out to be false then I'll retract it. I'd advise you visit your plumbing supply store and ask them about it.
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Old 12-12-2012, 01:40 AM   #29
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Originally Posted by der Mond View Post
Ratchye are you still listening? I live in Alaska also and if I could get verification from you that your solution is still working it would greatly ease my mind...Mine is freezing up at -10 and we can get to -60.
Still listening!

After "solving" the problem - multiple times, we're back to square one. We have tried:

*Insulating the pipe from bottom of attic to top, and
*Not insulating the pipe

*Purchasing two 90 degree caps (the "candy cane" method), and
*Then taking them off again

*Widening the problem vent to 4" AND dropping some serious cash to install a second 3" vent in case overload was an issue.....BUT

No luck. We did make it through last year without too much problem - maybe Mother Nature was looking out for us - but the moderately cold Alaska temps last week (down to -15 or so) have left us in the same predicament I posted about almost 4 years ago.

Read through the threads to see if any new inventions had cropped up, but nothing. Am now considering either the Arctic Vent OR the potential of lining the inside of the roof vent with a material that is freeze resistant (researching: extruded polystyrene foam insulation).

Any new, great ideas out there?

Ratchye


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Old 12-12-2012, 09:38 AM   #30
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Here's my theory. The water in your traps and in the sewer main (or septic tank) is gonna be cold by human standards, but it's still warmer than ambient. So, it's gonna steam. Maybe not clouds of visible steam, but a wisp of moisture nonetheless. This warm, moisture-laden air rises. And when that moisture hits the colder section of pipe that sticks up above the roof, it condenses and freezes.

Seems like there are some options:

1. Keep the pipe above the roof 32F or more.
2. Keep the moisture from reaching that far.
3. Use mechanical/chemical means to keep the ice from building up, or make the ice break off by itself.

#1 we've covered, typically electric heating.

#2 Maybe a flap in the pipe in the attic that closes at zero pressure to keep the moisture in and opens at either negative pressure (toilet flushed) or positive pressure (escaping sewer gas)? Probably no such thing made, and wouldn't pass code if fabricated.

#3 might be coating the inside of the with Rain-X, wax, petroleum jelly, or similar substance.

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