We installed all new drains and vents in our bathroom reno. The problem is with the draining of the tub. I will fill the tub and it will not drain for several hours. We had removed an iron pipe stack and replaced it with plastic, and had found that when the toilet didnt drain that bits of the old pipe were blocking the exit in the basement. We removed the blockage and thought our problem was solved, only to find that the tub still doesn’t drain. We installed vents from the tub, from the toilet and from the bathroom sink thinking that that would certainly solve the problem, and still the bathtub will not drain. My husband thought perhaps the pipe from the tub is not angled enough, could this be the problem? Please help, I do not want to take out the floor again!!
Do I understand correctly that the original installation did not include vents? If this is correct, whomever did the installation is wholly incompetent and there is no telling what kind of mess is buried below. It sounds as though you still have a blockage in the line. I would bring in a plumber who can scope the line and tell you what is going on. I would NOT use the same company that did the installation.
Improper slope of the tub drain may be a problem, but that should not cause the toilet to back into the tub.