Periodic qualification for water system

hi all, need your help

our water already been qualified successfully until finish phase 3. after one year, did we need to do periodic requalification?
if no, did we only need to provide chemical and microbial monitoring data to auditor? is that enough?
if yes, how should we do it? what test should be done ? and can we do internally or need to take external party to do?

thanks in advance
Safni Jimat