My goal is to remove as much defunct plumbing as possible.

My scenario is:

  1. Former sink in basement (removed), drains to septic under slab
  2. Current sink in kitchen, drains to septic through long pipes spanning much of house
  3. Vent for former sink drain is accessible via basement. Vent for kitchen is inaccessible behind kitchen cabinets/drywall. Both meet behind kitchen drywall, joining into single vent pipe exiting out roof

Here's a crude drawing (everything hidden but foundation wall and DWV pipes): current plumbing configuration

My plan is to cap the defunct drain pipe near the slab. Ideally I would then remove the corresponding vent pipe all the way up to where it joins with the kitchen vent, but that's not really feasible because I would need access behind drywall and cabinets in the kitchen.

So my next-best idea is to instead modify the defunct drain's vent pipe -- which happens to pass right by the kitchen sink's drain pipe -- so that it joins (and terminates in) the kitchen drain pipe, like this:

proposed plumbing configuration

This seems like it would be acceptable since a similar approach is taken for long drain runs to prevent siphoning (multiple vents on a single drain).

The new sanitary tee might have to be a Fernco depending on how much wiggle room I have. Other than that I think this would be a straightforward modification. Can anyone confirm whether I am on the right track? Thanks!

1 Answer 1


Yes, do it just like you said.

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