Thanks for the great feedback, that helps a lot. Yes, I meant that TDS was 1000.

I'll probably do the 25% at a time solution, although the plastic trick is a really neat idea. I figured out last night that the water doesn't cost any where near as much as I feared, which is also reassuring.

Michael, I've seen bleachcalc and wanted to give it a try (sounds great), but I guess that's one of the (few) drawbacks of being a Windows-free household.

cheers,
Scott