F1 fan
New Member
I haven't found an answer to this problem although it's happening more frequently. Back to back toilets on the 2nd floor worked OK with 1980 units. They were upgraded to TOTO Drake 1.6 and now a flush empty's the adjacent toilet bowel. I think this is going to cause problems with sewer gas and it's a rental property. There isn't any attic (flat roof). I believe the vent is 2" and was checked by a local plumber. Is there any reasonable solution without tearing the wall out.