Cleaning validation in the diagnostic industry

As I’m working in the diagnostic industry we have problems defining our acceptance criteria for cleaning validation, because the common calculations regarding patient impact do not work. As it is difficult to find out alarm limits for the huge amount of products I’m looking for a standardized approach for the determination of limits.
Question 1: Has anybody here the same problem and can provide an existing solution?

We are using aqua purificata for manufacturing. For that reason we are thinking about using alarm limits for aqua purificata according to USP (500ppb).
Question 2: Are there any experiences using aqua purificata alarm limits for cleaning validation?

Question 3: Are there any standardized calculation formula for conductivity?

Thanks in advance,