Connecting to vent and sewage stacks.

[Stan Ley]

Attached photo illustrates sewer system connections in my basement. I’m planning to install sewage basin system underneath the main sewer stack; 4” metal pipe going into the concrete yellow wall. I have a couple of plumbing code questions.

1) Would it be per code to vent sewage basin system, 2” vent, to vent stack (blue encircled threaded potential connection) below tee-wye, p-trap, servicing washing machine and dishwasher?
2) Is there minimal vertical extension requirement (depicted in red) above main 4” sewage stack for sewage basin system discharge that meets the code? White 4” x 2” wye below depicts my intended connection.

I’d appreciate your professional feedback. Thank you in advance.

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[breplum]

Not the blue circle, but you would have to make the vent connect above, in the vent section.
Drain connection looks proper.

 

[Stan Ley]

Not the blue circle, but you would have to make the vent connect above, in the vent section.
Drain connection looks proper.

Thanks for your comments.

Ok, vent connection above the wye servicing washing machine would be proper? Any idea/opinion why the blue circled connection was originally provided for?
This is over 50 year setup. Has vent code changed since then?