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So my toilet only flushes down during the summer months. Yet during winter fall and spring it wont go down all the way. Can't figure out why. Tried a snake and every other means to unclog but I doubt its clogged.

I'm in Michigan. summers are usually 80 or a little higher. 50 60s in fall and spring. and as low as-1 in winter.

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    Just a comment because I really don't understand plumbing vents. But it sounds to me like maybe the vent is getting clogged seasonally. Where are you? And/or what is typical outside temperature during "summer OK" and "winter fall spring NOT WORKING"? – manassehkatz-Reinstate Monica Oct 16 at 0:50
  • Septic or municipal sewer? What's the age and type of the plumbing? Any odd layout issues in the home? Please revise your question to add detail. – isherwood Oct 16 at 15:03
  • Have you tried filling up your toilet with a bucket and flushing? You have a couple of answers that might help but you need to do some troubleshooting. Fill a up your toilet like 2/3s of the way (yep that's a lot of water) with a bucket. Do this at least 5 times and tell us how it flushes. – DMoore Oct 16 at 15:10
  • Is there any type of cap on the roof vent to prevent debris from accumulating in the pipe? Do you have a lot of trees whose falling leaves can reach your vent? Squirrels/rodents? I cannot see ice being a problem 8-9 months out of the year, but it could be a factor in the winters. – peinal Oct 18 at 12:32
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This screams frozen vent stack.

To keep your drains flowing, you need to equalize the pressure. The problem is your sewer lines contain harmful gasses you don't want in your house. As such, you have a vent stack, a common drain pipe that allows gasses to vent out of the roof.

In deep winter (i.e. well below freezing, which is common in Michigan) what can happen is that the warm(er) water has some vapors that will head up the stack. Due to the extreme cold, the vapor condenses as it leaves the top of the stack. It then strikes the cold pipe, freezing to it. And now this makes for a nice perch for snow (image source)

Frozen vent stack

There's a couple of things to do

  1. Insulate the vent stack pipe inside your attic. This helps a bit in that the water vapor loses less heat as it ascends.
  2. Install something designed to keep the vapor from freezing to the top of the pipe. There's a number of products that do that by either passively absorbing heat from inside your home and transferring it up, or by being made of material that absorbs solar heat to keep the surface above freezing. You can also install a traditional pipe heater materials at the top.
  • Sounds like the problem occurs long before this type of frost would accumulate, though. You need consistently cold daytime temps. – isherwood Oct 16 at 13:22
  • @isherwood Depends on where in Michigan, though. Some parts can freeze like this in fall and spring – Machavity Oct 16 at 13:23
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    OP said spring and fall are 50-60 degrees. I just don't see it happening like this through such a wide swath of the year. I'm in the most brutal part of the US and it's rare even in January. – isherwood Oct 16 at 15:01
  • I just gave you a +1 because that picture is ridiculous. How did you find a picture of snow only in the vent stack? I wonder if they used a snow cone machine for the picture? – DMoore Oct 16 at 15:09
  • @DMoore, that's frost, and it occurs when warm moist air rises through the vent system and condenses and freezes when it encounters sub-freezing conditions above the ceiling line. The humidity of the air outside can be below the dew point, so no frost forms from it. Stop by and I'll show you a photo of my beard after a walk in -20F. It looks pretty much like that. – isherwood Oct 17 at 13:14
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this is more of a suggestion than an answer, but I think you should go to a big box store and buy a new toilet (a good one). Install it in the winter and see if it solves your problem. If it doesn’t you can return it and know that it’s something beyond the fixture. I had a friend who’s toilet was bubbling and we thought it was everything else... needless to say we changed the toilet and it solved the problem.

  • Why would an indoor appliance be affected only in cooler weather? This is a dramatic and expensive approach to an unknown problem. – isherwood Oct 16 at 12:55
  • I’m sure the other suggestions here are probably good ones, but for zero risk (because you can return it) you can try to see if the toilet is the problem. I would try that before I ripped up any walls or touched my venting. It would sucks to go through a bunch of work only to find out some cheap or old toilet cant function because of a slight pressure change. – Steve Oct 16 at 13:11
  • Someone has to pay for that toilet going from new to used. You may be comfortable tossing that cost to someone else for a weak reason. I'm not. Doesn't matter who it is. And no one has suggested ripping out walls. – isherwood Oct 16 at 13:21
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    Good toilets are less than 200 and take 30 mins to install. It isn't a horrible idea. – DMoore Oct 16 at 15:07
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    There are much simpler ways to run this test, like lifting off the current unit and seeing how well water drains directly into the waste pipe. – Carl Witthoft Oct 16 at 17:21

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