Is this related to SDR in ISO standards

In a way it is but not exactly. ISO uses SDR and ASTM uses scheduled piping. Schedule 40 and 80 is not rated in SDR units, at least for smaller pipes. Sch 40 and 80 pipe have the same outside dimension but 80 has a thicker wall thickness. But in SDR, a higher number rating is lower pressure while in ASTM, the higher number is higher pressure piping.

I hope the link below will help you.

PVC and CPVC Pipes - Schedule 40 & 80 (http://www.engineeringtoolbox.com/pvc-cpvc-pipes-dimensions-d_795.html)

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, Thanks.

John

Pipe schedules are a measure of pipe wall thickness. These requirements exist due to specific factors within certain applicable systems. Predominately, where pressures are higher, the schedule #, or actual wall thickness, is greater; to withstand the internal pressure of whatever liquid or gas is passing through. Schedule 10 wall thickness is thinner than Schedule 40 wall thickness.