Vinny, I have to tell you, most of my experience with sterilizing and sanitizing has been with things for sterile pharmaceuticals. I therefore don't really believe that a hot tub can be sterilized completely, since contamination can be reintroduced on a continuous basis. The tub is not a closed system.
Critical factors are as you say, the amount of disinfectant or sanitizer, what sort of organism you are trying to kill, the actual level of contamination [glb]and[/glb] contact time with the disinfectant
To give you an example, chlorine is a very good disinfectant and for many types of organisms it is bacteriocidal (it kills them) There are some organisms that are resistant however and therefore the chlorine may act as a bacteriostatic agent (it keeps them from reproducing, but they may still remain viable until conditions are favorable for replication-like a drop in sanitizer levels). To me something that is sterilized is void of ALL microorganisms. I don't think that is possible in a hot tub in a normal situation.
Just to see what happens, since you have me curious too, I am going to plate my water. It has been crystal clear and the bromine levels are relatively low. I'll try testing after shocking when the levels are high and when they decrease. since I only use strips, we will be limited to relative levels, but we can see what happens..and I will even plate after we soak, but before a filtration cycle... this sounds like science fair material
