First off, Thank you and God Bless to you and your husband for serving our country, I myself am getting ready for a trip to the desert, and I am in the process of looking for a qualified friend to loan a tank to. But any way,,,,
Something to think about that might make life easier, Perhaps you can set up a pump system allowing you to simply siphon out some water, and pump fresh new water back in, then all you would have to do is roll out the hose.
I am not sure if anything like that exists, but I am sure you could rig something up, for not a whole lot of money.
I think something like this would be very benificial in your situation.
This may even pay for its self in the long run, as you would not be paying LFS
to come out and do it.
Just a thought
Perhaps some of the old salts know of something,