Madpotter,
I use room temp filtered water to mix my VSL#3 mixture with the slippery elm powder. Why room temp water?
I guess that's personal preference, it was so long ago... Now that I think about it, I had tried cold water from the fridge, and it didn't mix as well and I also didn't like the feeling of drinking cold slimey concoction. I wouldn't use hot water because that would destroy the VSL#3 probiotics (remember they need to be refrigerated).