Least worst way to plumb in new sink waste

[Ben-gee]

I’d say that if something dropped into the soil from the top, right close to the pan, it will be easily moved on by the next full flush!

Coming in too low on the side leaves you far more likely to get paper/solids catching on the bossed in junction and therefore potentially building up and blocking the small diameter pathway you are trying to use for the sink etc.

I did say that this whole scenario is sub-optimal, I personally would find another route to waste even if this involved digging up the floor that the OP said they didn’t want to do.

 

[PythonCrazy]

So, I solved this with a pan connector with boss attachment per Ben-Gee's original suggestion. I was able to get the boss positioned vertically and drilled through the tiles above the soil pipe so the waste is hidden from view by the cistern and I have a happy customer. It also means that if anything catches and causes a blockage, it's likely to be accessible without breaking open the wall again.