The water systems in hospitals are notoriously poorly run and may not even be filtered in the distribution tank. So these days it would not surprise me to see any type of microbial recovery from the hospital scenario. I think if you have purified water system that is maintained the way the pharmaceutical industry typically maintains it with good wind filters and good processing and good engineering, you will not have aspergillus or mold recovery from your water system. Now I did say if you have aspergillus that it had to have come from outside. There is a possibility that if the wind filter is faulty or ruptured and you don’t know about it then the tank is actually aspirating or sucking in environmental air anytime the level draws down in the tank. You could suck in aspergillus or mold from the environment and if it is an ambient system those organism will float around in water and survive for a period of time until they eventually get flushed out. You will not have these organisms growing in the water system. So normally if you do encounter these molds or bacillus, they are almost certainly coming in during the sampling process.
