Basement bath venting adequate?

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New Member
Sep 14, 2020
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Columbus, Ohio
I‘ve got a very small, 50+ yo house with an unfinished basement with a ”utility bath”, ie the shower is exposed and just drains into the floor drain, and the main stack from the 1st floor toilet is out in the open. So the current setup is the PVC main stack (which is close to the outside wall) coupled to the original cast iron pipe close to the floor, which connects to the main drain under the slab which goes across the floor to the opposite wall. Starting at the top, the main stack starts with directly draining the 1st floor toilet, then there’s a 2” cast iron vent pipe (to the roof) about 15” to the left connected to the stack by a short horizontal section. The next two pipes connected to the stack are the drains for the 1sr floor sink and shower. About a foot from the floor is the 2” pipe draining the basement utility sink, which is about 20” to the right of the stack. About 25” away to the left of the stack Is the toilet, and another 20” away is the exposed open floor drain. When I replaced the old toilet I saw that the toilet flange was connected to 3” pvc pipe which looked to angle to the main drain pipe under the slab to probably connect with a wye.
So I’m wondering if this is adequate venting for this setup. When this house was originally built the vent only had to supply the toilet upstairs. The upstairs had a toilet but no sink or shower. And no toilet or utility sink in the basement, just an exposed floor drain. I’m asking because I’ve noticed on occasion that the basement toilet will make gurgling noises, which I assume is from using the other fixtures, but also rarely not flush quickly as it usually does. The vast majority of the time everything works great without any issues whatsoever. Could I possibly also have a blockage causing this? If inadequate venting any suggestions?


Staff member
Supporting Member
Jan 20, 2018
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Boston, Massachusetts
if that cast iron vent is in the basement your slop sink should have a vent connected between the trap and the main drain connect to the vent in the basement

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