Stainless steel or PVC pipes in water system?

It is the norms that for pharma water system, we require SS316L, internally polished to less than Ra 0.8 micron, for piping from the purification stage to storage tank of purified water and to the distribution loop.

Some may go beyond this to have the same pipe quality for piping in betwen the RO system. While this is acceptable for RO system, we cannot assume the same to be for a DI system, especially a twin bed resin system.

Why not?

The simple reason is due to the requirement for self-regeneration for a DI system. Acid, such as hydrochloric acid, and alkali, such as sodium hydroxide, will be used to regenerate the resins. As we know, acids & alkalis are simply corrosive to SS pipes. This serve to place high risk to the purification system itself and to the quality of the output water .

So, be conservative and stick to the usual cheap PVC pipe for connection in between the DI unit. Don't simply overdo and put your own water system at risk.