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 frozen vent stack
Author: Anonymous User

I LIVE IN NORTHERN WISCONSIN WHERE IT GETS PRETTY COLD AND MY ROOF VENT KEEPS FREEZING.THEN IT DRYS UP THE TRAPPS AND ALLOWS THE SEWER GAS IN.THE HOUSE IS ONLY 3 YEARS OLD AND I HAVE HAD THIS PROBLEM FROM THE BEGINNING. THIS YEAR I CHANGED THE VENT FROM A 3 INCH TO A 4 AND IT SEEMED TO HELP A LITTLE BUT IT STILL FREEZING.ANYONE HAVE ANY SUGGESTIONS.

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 Re: frozen vent stack
Author: Anonymous User

Why is a vent freezing, there shouldnt be any water in it. Im confused?

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 Re: frozen vent stack
Author: hj (AZ)

When you increased it to 4" did you start the 4" at least a foot below the roof?

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 Re: frozen vent stack
Author: plumbhelp (MA)

not only should the increase in size be at least 1ft. below the roof line, but the vent should also be at least 18" to 24" above the roof line where the vent goes through the roof.

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 Re: frozen vent stack
Author: Barry (MI)

RAISE THE VENT SO IT'S WELL ABOVE THE SNOW LINE ON THE ROOF. IF THERE ISN'T ANYTHING TO COVER THE VENT THEN THERE ISN'T ANYTHING TO FREEZE.

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 Re: frozen vent stack
Author: Anonymous User

YES,IT IS ABOUT 3 FEET BELOW THE ROOF LINE AND ABOUT 18 INCHES ABOVE THE ROOF LINE.I AM ON A SEPTIC SYSTEM AND IT SEEMS TO ME THAT THERE IS NOT A ENOUGH AIR FLOW TO KEEP IT OPEN WHEN IT GETS REAL COLD,BECAUSE THE HEAT FROM THE SEPTIC TANK SHOULD KEEP IT OPEN.I AM WONDERING IF SOMETHING IN THE SYSTEM IS NOT VENTED RIGHT.THANKS FOR REPLYING.

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 Re: frozen vent stack
Author: Anonymous User

It's condensation coming from the septic system that is freezing. If you can wrap insulation around that portion of the vent in the unheated attic it should help a lot. I have seen steel casing used as an outside flue for a wood burning stove that would freeze up from the moisture in the flue gasses. Fiberglass insulation wrap with a sheetmetal sleeve stops it.

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 Re: frozen vent stack
Author: plumbhelp (MA)

good idea joe.

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 Re: frozen vent stack
Author: hj (AZ)

In the Chicago area the vent was installed 12" above the roofline and then a lead flashing was installed around it which allowed the attic heat to circulate around the exposed section of pipe.

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 Re: frozen vent stack
Author: steve (CA)

Rbill, how about wrapping some heat cable around the area that freezes?

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