For the ceramics, the integrity of the purifier medium is important.  Well formed and free of flaws, the purifier should have good strength.  There is a crude indication of strength when one scratches the purifier with a fingernail or a sharp metal object.  If some material comes away the purifier is fragile, more subject to breaking and wearing.  One could think of desired durability as that which would give a purifier that is as 'hard as a brick'.  Good strength should also be an indication of longevity of the purifier. 

Colloidal silver aspects of production need consistent assessment.  The CS used for purifier saturation should be monitored for parts per million.  New production runs of purifiers should be initially tested for the presence of silver in the filtrate, a double check that the ceramic is retaining this disinfectant.   And for particular communities, where the purifiers are in use, it will be important to followup over time, to make sure the proper steps are being taken, which ensure people are getting clean water and not getting sick from water.  Once the purifiers are doing their job the only cause of failure may be some lack of hygienic practice.

New projects in pottery candle production may want to conduct some initial tests for longevity.  For the ceramic this would be especially true if the strength were other than the optimal, 'hard as a brick.'  Accelerated flow testing would be useful in reducing the time necessary to determine longevity.  For example, if the column height of water is increased so as to double the normal flow rate, then a project could learn the longevity within half its duration. 

As to presence of silver in the filtrate, what should be expected is that any silver that is not well situated within the medium will come off in the early stages of flow testing.  The expected behavior would be a diminishing amount of silver in the filtrate, so that after a short period of the initial testing per production run the purifiers could be used in households.  After a bit of fine tuning as to appropriate permability of the purifier, in relation to particle size of colloidal silver, and other parameters, further random testing would become less frequent or unnecessary.  It is important to note that such ceramic and water quality tests are key to any project, especially in the beginning.  Appropriate tests over the longer period need to be identified and put in place.