Thank you Linda.
I just turned on the engine and the water pump, and water went through faucets after a couple seconds, shower and faucets ran fine. But without engine on, the water pump won't run. According to my control panel, my battery is low. (It means house battery, not car battery, right?) Not sure if it's misreading battery levels, because it can barely detect that my fresh water tank was nearly full.
Also there are two exterior drains, both on driver's side. One is what I believe is a water hookup (when I turned on my engine + water pump, it spilled out what must be fresh water, until I turned off water pump). I need a cover for that, to stop the spillage. The 2nd drain is looks like it's meant for convenient drinking water. Its old and broken and I had to use a wrench to set the plastic switch to off, so my water doesn't spill into the ground rather than my sippy cup.
So...is my battery actually dead(ish)? Or could the control panel possibly be deactivating it to preserve it from a full death? Questions, questions.