Mesuring conductivity of purified water

While there is a conductivity meter already installed at the purified water generation system, the absence of on-line conductivity meter prior to the entry point of return loop (to purified water storage tank ) is somewhat not acceptable.
No matter how technically good the purified water generation system is designed with SS 316 water distribution loop with electro polished pipelines (>20 mm diameter), sanitary joints, adequate slope with no ‘dead legs’, but a NO check to conductivity at return loop may jeopardize the overall water system.
Conductivity increases with increase in ions - CO2, pH or an increase in bio-load which is an indication of deteriorating quality of purified water duirng its journey in the loop. This must be checked at all the levels and re-confirmed by testing conductivity at return loop. Therefore, the position of conductivity meter at return loop is most justified.

Re-qualification of LAF - Possible requirements

When one of my frined enquired about re-qualifcation requirements of LAF for any reason, it was easy to reply - Hey buddy, go for velocity, linearity, leak test(DOP Test), no. of air changes , temperature and humidity. That's true, these are all the requirements when a LAF needs to be re-qualified, say after re-installation, major maintenance or replacement of major component (e.g. blower).
But let's take a deeper look. In fact re-qualification of a LAF should not be taken as differnet from initial qualification. In case of equipment used in sterile areas (or other wise too), the re-qualification should follow the initial qualification protocol or practice. The point is new DQ should meet new user requirments. The other critical attributes such as velocity, linearity, leak test(DOP Test), temperature and humidity (If requirement are specified) must be addressed with acceptance criteria clearly laid down. However, what is important in this case is the area qualification where the re-qualified LAF is (re-) installed. For this routine area monitoring for vialbe and non-viable particluates can be performed.