Can someone comment on the plumbing in my basement half bath. It looks like the sink and toilet both wet vent into the main stack which drains the bathroom located directly above (all the fixtures upstairs drain to the main stack). I have included a picture. from this forum, I understand that wet venting between floors is not allowed. The toilet seems to flush OK and there are no smells coming from the sink so I think the trap is intact. Would flushing both upstairs and downstairs toilets at the same time cause problems? Would the water from the upstairs toilet block the "vent" for the basement toilet if both were flushed?
I think the plumbing upstairs is vented correctly as I can see them tying in together in the attic but it seems like there are no vents from the basement. I plan to upgrade to a full bath in the next year or so and I assume that I will need to run a dry vent from the basement through to the attic and tie it back in.