Water Filter Storage

I have one. I just unhook it and let it drain. Actually, over the winter I brought it inside the house and it's under the bathroom sink. I left both ends open to dry out, not stay wet. Keeping it wet will encourage bacteria to grow. Let it dry out. When hooking it up the next time, run some water through it first for a few seconds to discharge any dust or anything that might have settled in the ends. Also, get a new filter (if you're talking about those disposable ones), at the beginning of the camping season, and just stow it with your water hoses. This works for me.