I want to create indoor water storage for chlorine contact time in a small public water system out of 12 inch pipe in a vertical switchback configuration. It will stand on end on a concrete floor and be bracketed to a block wall. Will sch 40 PVC be sufficient or is sch 80 necessary and why?

Here is some info
PVC is for drainage and cold water lines. CVPC is for hot water lines.
Schedule #20 is used in lighter applications with not much pressure.
Schedule #40 is the most used in water piping and drainage.
Schedule #80 is used in applications that require a heavier stronger pipe such as a commercial contract would call for, I hope this will help you, Thanks.

John