PVC is a thermoplastic, and therefore, at some point it will begin to degrade and break down as it's heated up. It just so happens that Schedule 40 PVC's maximum operating temperature is 140 degrees Fahrenheit, around the same temperature that hot water gets to in most homes. That max operating temperature of 140F means that any temperature above this will cause the schedule 40 PVC pipes to break down, compromising the integrity of the pipe (think leaks and bursting).
For this reason, it is recommended that PVC pipe and fittings be used only for applications where the water temperature does not exceed 140F. Even if your application involves water at temperatures nearing 130F, I would recommend another material, as temperatures have a tendency to fluctuate, and it's always better to err on the safe side.
So what's your alternative to PVC for hot water lines? CPVC
CPVC is a thermoplastic just like PVC, and it comes in pipe and fittings just like PVC. The difference lies in the chemical makeup. CPVC material goes though an extra chlorination process that gives the plastic slightly different qualities - one of which is a higher maximum operating temperature. CPVC (schedule 80) pipe is rated for use up to 200 degrees Fahrenheit. This makes it ideal for use on hot water lines in homes and businesses.
Source from: https://www.pvcfittingsonline.com/re...for-hot-water/