I am in the process of replacing floor tile in my basement bathroom. We moved to this house (built in 1950) a couple of years ago so I don't have a lot of information on previous renovations. I estimate the basement bathroom was built between 15 and 20 years ago. I removed an old american standard rear outlet gravity toilet and noted that a bit of water was coming out of the wall drain. I have it plugged now with a 3" plug to stop the water. I opened the wall on the other side of the bathroom to see the drain (fortunately I only needed to remove a panel - see attached picture). As you can see, the toilet is very close to the main drain of the house.
I would appreciate help with the following questions:
1 - Does the installation shown in the picture is done correctly? The pipes drain and vent a vanity and the rear outlet toilet I mentioned earlier.
2 - We heard the old toilet "flushing" by itself several times a day. I was thinking that replacing the flush valve and reinstall the old toilet, but now I am wondering if the self flushing has to do with water getting in the toilet from the drain line.
3 - Similar to the question that started this thread, I measured the distance between the concrete floor (I removed the old ceramic tile) and the center of the drain and it is exactly 4". The tile that I am installing now is slightly thicker than the old tile I removed. I estimate that when the floor is installed the distance from finished floor to the center of the wall drain will be about 3.5". Will the rear outlet toilet still work?
4 - Do you recommend replacing the old gravity rear outlet toilet with a new pressure assisted AS Yorkville or the Kohler rear outlet?
Thanks in advance