Originally Posted by CanoeStream
Flush the traps well with RV antifreeze.
Spend a tiny few $$ and pour some cheap vodka into the emptied fresh, gray & black tanks if those worry you at all (thanks 2airishuman!). Though I usually think that an inch or two of water in the bottom of these tanks can't damage them.
I should have reversed that order. Put the vodka into your gray through one of your drains. And then flush a solid slug of RV antifreeze into the trap. 2-3 cups all at once seems to be adequate to me.