Bonnir:
My wife would shoot me if I even thought of dividing in the house, I set up a potting bench and shower head out back that seems to work fine. I agree with jerry I thought that was the only way to do it. Can I get some of you ladies to talk to my wife, cause it gets cold out there when I usually divide in early spring. I'm in the process of building our retirement house in Virgina on the Chesapeake and one of the things I designed was an outside shower/potting bench/fishgutting bench, etc. and it will have hot water...
. I'm still deciding on how I will put in a pond I have a circular drive with a 35' dimameter and I'm thinking of making the interior of the circle a pond (albeit I will have a 2' apron, because DW would probably hit it with her SUV!).
I'm sure that it is better to divide hardies in the Spring, which I learned from some hybridizing heavyweights such as Pat Nutt. The key is to get some root growth before the pond freezes. This will give the tuber more strength to survive the winter. I usually divide when the pond hits 50 F (BRRR) in the spring and they take off once the pond temp hits 65F.
I agree most water lilies are like weeds and you would be hard pressed to kill them. However, a few varieties that I have had over the years are pretty finicky.