SpudFiles

Pressure rated ABS is even better for pneumatic than rated PVC

non-rated ABS is usually cell core, cell core is full of bubbles and hardly any measures are taken to ensure its strength, so non-rated ABS < plastic water bottles

I doubt that your system will have constant pressure I can't think of many situations where that would be the case, there is a difference from constant flow and constant presure

Where do you live?

In Ontario, almost all of the ABS is solid wall, while cellular core ABS is very difficult to find.