Patriot Medik-Aire HEPA Filter....
Bill, I have used this dome HEPA filter for Tri-Stars that you have. It is sold under 2 names, VacFx & DustCare. I use it in my Miracle Mate, as there's no way of using a external filter with it besides the Technostat filter it's designed for.
I have noticed the same thing as you & Jason....performance seems to be normal when using it. However, I can't attest to whether it captures EVERYTHING though....I bought it last year, used my Miracle Mate as a driver for about a month, put it back in it's box & haven't touched it since. I didn't bother checking behind the filter to see if there was dust on the motor itself or if there was dust on the back of the filter. So, I guess we will have to take Jason's word as evidence it doesn't leak, unless someone else here says otherwise.
My only concern about using this dome HEPA filter is that you don't get much material for the $15 to $20 dollars that most shops charge for it. So, even if it does capture all the dust particles down to 0.3 microns that pass thru it, thus making it a Sealed HEPA System, how long would it maintain it's full efficiency? If I remember oorrectly, the filter is supposed to be changed every 6 months; if that's true, that says a lot about how long that filter keeps it's efficiency.
If I could make another suggestion....buy & use the Patriot vacuum's Medik-Aire HEPA filter on your TriStar. Yes, the initial cost is high, but the filter lasts for 3 years according to Patriot's manufacturer. And the filter is HUGE too I might add....I personally think that if the filter bags are changed regularly, & the cloth bag & dome foam filter are washed & maintained on a regular basis, the Medik-Aire HEPA filter should last at least 5, if not 6, years in normal household use.
The online retailer I linked to below, Oregon City Vacuum, is selling it for $135....whereas SREC is selling it in their online store for $199. $135 stretched over 5 years seems a reasonable cost to me. Check it out & give it some thought.
Rob
http://www.oregoncityvacuum.com/patriot-medik-air-hepa-filter.html