This probably sounds obvious, but have you used just straight vinegar and let it sit for a while? I have this problem as well and I have to use filters on everything - even my coffee pot, because of it. I always buy several gallons of store-brand vinegar at a time, just for cleaning. Even doing that, it is still cheaper than other (more harsh) options and for me it is more effective. To clean: I flush my toilet and then, while the water is low, I pour in a good bit of vinegar. Don't be conservative here, especially if you have built up stains, really pour it in. That way less water comes in the bowl and the concentration of vinegar is stronger and more effective. Make sure you pour enough that the water line (of vinegar) is just slightly higher than the stains. Then walk away. Let it soak for as long as your family will let it. :) Then go back and scrub. As bad as my toilets were, that has worked every time for me. Good luck and happy scrubbing. :) *Also, when you flush the vinegar smell will go with it, so don't worry about that.*