I have a ground flow toilet that just flush, and drains very slow. I have snaked the toilet, and through the clean out in the basement. The bathroom and kitchen sink are on the same drain line before the toilet, as well as the dishwasher. These all drain fine. I noticed while I was in the basement working on the problem, that I don't have a vent tube on the drain line. I also noticed that when I run any other water on that drain line, I get air bubbles into the toilet.
I just came back from Menards with all of the fittings, pipe and etc.. I'm adding the vent here shortly. I bought an Oatly Vent that runs off of the line without being added to the rest of the Vent loop. Do you know if these work well or not?