How long will water from boiled potatoes keep in the refrigerator?
About as long as milk does.
It will change it's flavor as it stands in the cold, usually getting sweeter.
I always use it by the next day. I've been happy by using a poolish to start my potato bread overnight, so if I'm using the potato water from cooking potatoes for dinner, I let it cool to lukewarm, then make my poolish with it that night and bake the next day.
Thank you so much, I will toss it, it is a week old.