There is a huge difference between having medical instruments or containers made of silver, or even copper for that matter, as the concentration of metal is very high at and very near the surface which is what kills or prevents uncontrolled bacterial growth near/at the surface. That is not at all the same thing as killing bacteria in the bulk spa water. Your spa does not contain a fast-acting sanitizer, period, and there is continual introduction of new bacteria from your body into the water. Metal ions (silver or copper) do not pass EPA DIS/TSS-12 and I already gave you a link to a post listing numerous scientific peer-reviewed studies in respected journals demonstrating how silver at concentrations allowed in spas (below the limit of staining surfaces) is slow to kill bacteria and effectively doesn't control some of them, is completely ineffective against most viruses, and probably not effective against protozoan oocysts.
I have also contacted Dr. Bauer at the Mayo Clinic to see what he has to say about this.
His response should be interesting. Other than a bacteria test, how should I test my water? The human waste componants described don't get oxidized, and can't be due to the weight of the silver. They do turn into a tan colored fluff in the water and and a tan colored sludge out of the water. This I just suck up in the vac every 3-5 days. How can I tell if I'm putting myself in danger?