There is a door to the outside immediately behind and to the right of these tanks. I have an extra piece of PVC that I attach to run the water out the door. The downside is that I have to leave the door cracked open while I work, but it's so quick that it's not too bad.
Then, I take tubes (or tubes with gravel vacs depending on how bad the tank is) and start the siphon into the closest opening below the tank and let it drain. I do large waterchanges weekly.
For filling, I use one of those white RV hoses and have it attached to the shower in our downstairs bathroom. I have a garden hose Y connector with an adapter where the showerhead is supposed to go. That way, I have one branch of the Y for filling tanks, while I can leave the other attached to my RO system. Each branch of the Y also has an individual shutoff. One of the pics in this thread shows it filling a tank.
Since we still use this part of the house for occasional entertaining, I have to be able to clean up/hide all of my extra fishroom junk when needed. So, the hoses all get coiled up and tucked in the shower and the buckets go in the garage when we have folks over.