Welcome to our forum.
All of the answers lay here:http://www.whatsthebest-hottub.com/cgi-bin/yabb/YaBB.pl?num=1146236009/0Terminator
It is a [glow]fact[/glow] that with Hot Spring all of the water is filtered all of the time.
On another note, some companies DO have better filtration than others. How much better is hard to determine, but if there are different types of filtration systems, some will be better than others.
This a very fair statement but I think what is being said here is that most spas on the market today will adequately filter your water, some will make it easier and some simply are better but again most will keep your water clean.
It would be cool if a rating agency would get spas from all of the major spa companies and fill them up with dirty water and do tests as to what spa turned the water clear the fastest...
I know terminator had some pretty cool pictures on one post about a HS being filled by the Fire department with dirty water.... I think with in an hour they were bathing in the tub... Had pics of the filters after.... they looked pretty nasty...but the water looked great!!!!