On my last trip of the season on the way home, I open my fresh tank
drain. This allows most of the residual water to slosh out.
Since I use my pump to pump in anti-freeze later the pump is
protected. I wouldn't want to un-install it each season!
Some years that "last trip" doesn't happen due to bad weather or schedule so
the tank has a bit more water in it. I just leave the drain valve open
and have not had any problems. The drain line is about the size of a
pencil so unless we've got pigmy mice around here they aren't getting in!
FYI, most state police will frown on anything draining out of your RV
even fresh water. If you pull the plug on a full tank and hit the road
and a cop happens to be behind you, you 'll probably get tagged.
I let mine do most of the draining while we're tearing down on the last
morning before we head for home....