[Alberta's Child]

I don’t think it’s a venting problem . . . the drain pump vents directly into the building’s vent, and there’s no evidence of any odors anywhere else but in those two basement sinks.

[rdax]

from your post you say (Vanity), but you are not installing a vanity.

very misleading.

[lack-of-trust]

REgarding the vent, check to see if the sink trap is still full of water after the sink drains. A clogged vent can cause the traps to be “sucked” dry, letting sewer gas back into the building