My handyman hurt his knee and is out for surgery.

So, from my limited scope of experience here are my take-aways:Vinyl IS 100% waterproof because it is 100% plastic (actually, it's probably not technically 100% plastic, but in essence that is what it is). 

Hi,My friend is building a ~600 sq ft ADU in So Cal/Los Angeles and is wondering what type of pipe might be best from a quality/maintenance/cost standpoint within the interior of the ADU (I realize that the line connecting the ADU to the sewer line might be HDPE or some other plastic pipe...)? 

I’m convinced the former home owner is having elective brain surgery just to stay in the house a little longer but that is another story for another day :-).

For uppers, shimming can still be required, such as behind the steel support rail if the wall is horizontally wavy, or at the bottom of the cabinet if the plastic spacer they include isn't thick enough. 

Inside solutions like French drains, sump pumps, or plastic inside waterproofing might be fine for that 25-year storm, but the water is already getting in and damaging the foundation.

Was off work for 2.5 years due to back surgery.

Have them regrade and put rock/plastic around the foundation to shed water away.

From your first picture there is a plastic pane that slides into place so that it can stay closed/locked and keep the dog (or other animals) from climbing in and out.

Is the exterior basement wall covered in plastic wrap?