RVarley
I've used many many canister vacuums. The Rainbow is not the strongest of them but it certainly is not the weakest. I owned the newest Rainbow E2 Type 12 and it is significantly improved over previous versions.
Carpet grooming performance is beautiful.
That said I did have issues with the HEPA filter on mine. It would get clogged and DRASTICALLY cut down power. The distributor I worked for that I bought it from too didn't even really understand the issue of the HEPA clogging so he installed a new one for me on the machine, on the house.
It very well could be an issue with hard water in the house. I had terrible issues of scaling on the basin and separator. A hot water Vinegar soak was the best way I found at removing the scale. Dawn nor other dish detergents did anything for it.
About every 2 weeks I had to soak my separator, the nut and basin to the rim in hot water with about 8 ounces of white vinegar.
I would also recommend checking your HEPA.
I hope this helps you because in my experience of vacuums, this Rainbow really did impress me. Comparatively there are TONS of machines over the years I've tried and refuse to work with due to not meeting my fussy cleaning performance desires!!