<div dir="ltr">I'd still suspect your roof vent. Only time we ever had a vent problem it was caused by animals trying to nest in or on the roof vent. The plumber we were working with insisted that he could not cover the vent pipe with any sort of protector. So after he left I made a wire cage box out of stainless hardware cloth and never had another issue in the remaining 10 years we lived in that house. I made the cage significantly larger than the vent pipe. I think it was about a 2.5" vent and there was at least 3" or air space inside the cage on all sides. I put a small piece of sheet metal on the top of the cage directly over the vent pipe to keep any debris out of the pipe should birds or other critters decide to nest on top of the cage. When we sold the house the home inspector flagged that as not being to code, so I removed it and left it in the garage with a note for the buyer.<br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, Dec 7, 2020 at 7:26 AM Jim Franklin <<a href="mailto:jamesf@groupwbench.org">jamesf@groupwbench.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Maybe some of you have an innovative solution...<br>
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My house has a single cast iron soil stack that does both drain and vent. When I flush the toilet, it sucks air from the tub drain. The toilet and tub enter the stack separately, but at the same height, using an oddly specific T with a 4" toilet and a 2" tub inlet about 45 degrees apart. The tub does not have its own vent. 2 years ago I had a plumber snake the vent from the roof, he found "stuff", and it was fixed. Last week it started again.<br>
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My kitchen sink T's into the stack at knee height, so it's the highest item on the stack. My thought is, because it's a straight T, not a sanitary T, stuff from the sink is solidifying inside the T when the flow hits the back of the T, and eventually forming a cap of "stuff" just above the T entry, sealing off any venting. I can't tell if the sink is also being used as the toilet's vent because there are too many walls in the way to hear what's happening. <br>
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My other thought is that the "stuff" is growing like a mold, and sealing it off. Does stuff grow in drains? <br>
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Any thoughts on what it might be, and how to prevent it? I rarely put oils down the drain, and when I do they are cold and mixed with Dawn to emulsify it. There isn't enough canopy for leaves or squirrels to get in the roof vent. <br>
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thanks,<br>
jim<br>
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</blockquote></div><br clear="all"><br>-- <br><div dir="ltr" class="gmail_signature">=================================<br>= Never offend people with style when you =<br>= can offend with substance --- Sam Brown =<br>=================================</div>