Well I heard a rumour that there may be a possibilty that if you have an endotoxin filter on your machine (diasafe/ultrafilter) and it is changed within manufacturer's guidlines, then you don't need to test for endotoxins?

Anyone else heard anything similar?  It would save us a fortune in sampling costs.

We test our plant water every month and individual machine substition fluid every 6 months (after a 3 month blanket testing regime provided sufficient results to allow this) and we don't see any failures so what is the point in testing the HDF fluid any further?

Seems like wasted money to me.  If an incident or querie occurs then a sample can be taken to eliminate the water from the querie.  As long as the ringmain water is good and the filters are being changed and the "x" amount of previous years data proves it then why do it?