Adding a second drain into existing cast iron riser/vent

[TheOverThinker]

I need to add a second sink mirrored behind the plywood at the back of this sink, using
the same drain and riser.

What's the least trouble, mostly code acceptable, way to do this tie in?
Located in California.

I see this forum post: https://terrylove.com/forums/index.php?threads/horizontal-double-wye-for-two-sinks-kosher.69261/

For odd reasons, the sink will never be used, and both sinks will be torn out in a few years... so there's a reluctance to get fancy. At that point the entire under slab cast iron needs to be redone.

 

[TheOverThinker]

Your thoughts? I have read https://terrylove.com/forums/index.php?threads/horizontal-double-wye-for-two-sinks-kosher.69261/

 

[Sponsor]

 

[Jeff H Young]

2 sinks calls for 2 inch . looks like 1 1/2 vent an easy way would be cut the gavinized vent and install an 1 1/2 " abs spigot santee pointed oposite. but its not legal. looks like cast iron is coming thru a stem wall if its 2 inch perhaps you can do it right with out tons of work.
Im not suggesting the first method but Its been done and could be a way probebly no noticeable negative effect

 

[TheOverThinker]

ooks like cast iron is coming thru a stem wall if its 2 inch perhaps you can do it right with out tons of work.

It's 2" going down in cast iron, 1.5" going up as a vent. All from 1925.

There's no way to increase the size of the vent, and no practical way to run a new vent.


The stacked sanitary T's are a definite code violation.
How about the Y's as shown in this video?

 

[Jeff H Young]

This old house doesent look legal. You cant y off a trap arm and dump waste in there. video seemed to leave off how trap arm got to new sink .
Video I dont think helpful if your interested in legal.

 

[TheOverThinker]

looks like 1 1/2 vent an easy way would be cut the galvanized vent and install an 1 1/2 " abs spigot santee pointed opposite. but its not legal.

What would the code violation of that approach be?

There are a ton of double sink kits. Are any of these applicable?

I know they suck.
This is a temporary sink situation, if it last a year thats good enough.