Drain water filter?

Just got home from our 4th weekend trip in our 3011ds. I drained the hot water tank, and the low point drain. The thought hit me that I don't think I've heard anyone mention draining the whole-house water filter between trips. Mine is hidden in a closed compartment I the back of a basement compartment. I would assume that it's not a good idea to leave standing water in one of those for any length of time. I removed it , and water poured into the compartment. I thought I'd drained everything I knew how.
Any suggestions for this newbie?


Forester 3011DS