What schedule size pipe should you use in a 100' well,40 or 80?

Go with Schedule 80 PVC.

Milo

I agree with Milo,

Schedule 80 PVC pipe will work great, for more information open the link below, Thanks.

John

PVC Pipe Schedule 80 PVC Plastic Pressure Water Drop Pipe for Water Well Pump Setting

Well I would go with flexible well piping. Makes putting the pump down the well easier and makes pulling the pump a heck of a lot easier if you have to pull it in the future. More costly but worth it.

It is also a lot less likely you will drop the pump down the well if you don't have to put the pipe together of cut it apart while its in the well casing.