On the motorhome, you can't "pour" bleach into the fresh water tank. There is no hose fill hole. It's pressure fill only. You can, of course fill the hose with bleach, hook it to a source and push it in...
I *think* you're should connect to the inlet of the fresh water (female hose connection) via a special hose, arrange the valves, then use the pump to pump the water/bleach solution in.
Just waiting on confirmation.