I have a building with 3 floors (1 unit in each floor). When I flush the 3rd floor toilet, bubbles come out of the second floor toilet.
How do I stop 2nd floor floor toilet from bubbling? In general, is it not recommended that you combine drain stacks for bathrooms on different floors?
Here are some details about my house/plumbing:
My house has a basement, ground floor, 2nd floor, and 3rd floor (attic). The toilet in the ground floor has a ventless drain vent with a STUDOR valve at the end of the vent The ground floor toilet flushes without any issues, and drains properly It seems to me that what is happening is when the 3rd floor toilet flushes, the volume of air in the 3 story length drain pipe needs to go somewhere, and it is venting out through the ground floor toilet. Before, that air was going directly into sewer, but now that we added the ground floor drain to it (in the basement), the air is venting through the ground floor toilet. Does this sound correct?
Besides creating a new drain stack for the ground floor bathroom, is there a way to exhaust the air from the 3rd floor drain somewhere?
Thank you for your help!