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Can a basement bath (toilet, sink and shower) macerating pump system be workably (not codes) vented into a 3″ PVC that vents out the roof if the 3″ PVC vent pipe also has 2 vanity sinks on the floor above using the 3″ PVC for both a drain and vent (the sinks have traps of course where no smell at the vanities from the pump will exist; and, the basement pump vent will be hooked into the 3″ PVC from above it where no vanity drainage can drain into it); and, if done, what are the actual drawbacks? Is the only possible actual problem that the basement bath will not drain as well only when the vanities are being used?