Revalidation of purified water system

Dear sir, I want to know that if there is inclusion of sampling point in previously validated system, then how it can be re-validate? Should Re-validation to be done for only that new sampling point or for whole system means all sampling point? and also for how long period, it should be for one month? And during this period, water can be used for routine use or after completion of one month it can be used?

if you add a new sampling point only that point can be revalidated, sampling to be done for 7 days both microbial and chemical sampling.
water can be used immediately based on risk basis, but water should meet all the critical parameters like conductivity, return flow.etc…