I posted a questions a week or so back, I wanted to add something to see if it is related. When it is really cold out (0 or below) we get a smell almost like wet carpet in our basement. Wondering if this is also a symptom of a blocked roof vent. Here was my last question, just so you can see the other symptoms. Thanks

My question is regarding both toilets in my house. In the past year, they both have been running sluggish, and once every 2 months or so they will gurgle and then overflow. It seems to be the 2nd floor one mostly. My husband will use a plunger and it will still be sluggish, but won't overflow for another 2 months or so. A few days ago we got a toilet auger and used it on both toilets - nothing seems to be blocking in the toilets. The are one right above the other, and we have a septic system. Also, when this started to happen I also noticed a septic-like smell in my washer in the basement (the septic system is right in front of where the washer machine is). We are now thinking it may be the vent on the roof. The sinks or shower doesn't seem to be affected. Any suggestions??