Earlier this month, we starting having problems with our sewer line; it began with the downstairs toilet flushing very slowly, then not flushing at all, then backing up when the upstairs was flushed. After consulting with the previous homeowner (a contractor), he advised that the sewer line was probably frozen (we live in Fairbanks, AK). We called a thawing company, they can and steamed the line, and everything was copacetic.

Fast forward to two days ago. Same symptoms started appearing; very slow flushing downstairs toilet, but the shower and sink drains run fine. So, we called the thawing company back after plunging, running a closet auger down, etc.

They came out and found that the line was not frozen, and checked the vent stacks... One of which was frosted shut. They steamed both vent stacks, and called it a day.

Now, the toilet is still flushing very slowly. I'm not sure what else to troubleshoot; I'm now out almost $500 in steaming service, and I can't find a plumber that can come out until next week. Suggestions?

  • I don't think that block vent stacks would cause this issue. If blocked, what would happen is it would draw air in through the drains and you'd hear a gurgling sound as that occurred. It definitely seems to be a blockage of so sort past your downstairs bathroom. Beyond that, I'm sorry I have no idea since I have not dealt with frozen ground issues but others here will I'm sure and will comment soon
    – Ack
    Commented Mar 27, 2020 at 0:58
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  • Really How cold is it that your sewer vents are freezing this time of year? Have you tried boiling water just pour it in the upstairs toilet the water should force flush and may just do the trick. Commented Mar 27, 2020 at 5:19
  • You may want to also add a T made from copper pipe to stick in the top of the vent makes it easy to keep vent from freezing solid Commented Mar 27, 2020 at 5:52
  • 2
    I’m voting to close this question because it's been abandoned.
    – FreeMan
    Commented Dec 23, 2020 at 14:41

1 Answer 1


The lack of venting does cause the drains to flow slowly. In your case, mostlikely caused by the stack freezing again.

I would suggest you do one or a combination of the following:

1) Insulate the exterior portion of the vent stack. That way it is less likely to freeze during the coldest time of the year (one time fix)

2) Add a heating element around the top of the vent stack. I did a quick search and found a product called ArcticVent. This keeps the exterior and upper portion of the stack warm so that it does not freeze. (one time fix)

3) Pour deicer down the vent stack when it does freeze. Deicer would melt the ice. Obviously this would be a quick fix and you wouldn't want to have to do this often, especially if there is snow on the roof. (repeated and temporary fix)

  • 1
    Slow flushing again was within an hour of the stacks being steamed... With an ambient temperature ~30°F and bright sunlight; I don't think they're frozen over again. But I'm definitely going to add insulation or a heater to the stacks before next winter. Commented Mar 27, 2020 at 20:21

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