I know it's a bit too early for this, but I didn't want to forget to post it...
I've been doing a lot of web browsing, on my "Injury vacation" and I just came across this.. Using this mod, you can use your water pump, to pump a bleach solution into the fresh water tank. I wish Sunline had put the 1-1/2" drain in the fresh tanks, but they didn't. I'm not really sure of the best way to flush it all out.
By the way. this mod would also help people that dry camp a lot, get water into the fresh tank. A lot of dry-campers haul water to the camper, when they need it. With an extension on the suction hose, they could pump the water from the truck and not have to rely on gravity.
The pic shows the location of the crossover pipe and where the valves need to be..