Shower – Bathroom Toilet + Shower Venting Fitting Question

The new stack in the top right should connect downstream of the toilet. It can pass behind the toilet and then run parallel to the side wall to the corner. This leaves you with a wet vent via the vanity that servers the bathtub and toilet:

                     Vanity    New Stack
                       |          |
                       |          |
   Shower ------------\|          |
                       |          |
                       |   Toilet |
                       |/----     |
                       |          |
                       |          |
                       |/---------/
                       |
                       |
                       |

As a minimum, the wet vent would need to be 2” as shown on your drawing.

It sounds like you want to install a sump pump drain system so that the drain can be pumped overhead. I find that sump pumps generally last a few years... replacing the pump every few years is onus, and these sytems add a stink to the living area. If the septic or drain system is above the shower drain level (above the basement) then this is your only option, anyway.

But if the septic/drain system is down hill (gravity fed), then my advice would be to run the shower drain in an inconspicuous area and attach it to an available stack. If that is not practical or possible then my advice would be to cut the concrete with a water saw and install a drain; then you will need to lay new concrete over the drain... cutting concrete is kind of a major task... depending on the length of the drain, but believe it or not, I would still recommend going with gravity- over a sump pump for problem free plumbing that doesn't stink.

If you need to contract this job, then price-wise, your best bet may be to run the drain where it is not a tripping hazard (to a stack pipe). The next cheapest option would be the sump installation. Cutting the floor will cost labor... the most expensive part of a contract. But if you do try a sump pump, you can still change your mind later.