Can I gravity fill my on board tank?

Many rigs now come with wet bays and valves similar to motorhomes where valve selection dictates how/where water goes. Mine is similar in that I can fill the tank with a hose and use the onboard pump. I can also hook up hose and run off city water pressure. If I want to fill from a jerry can I hook up my short winterizing hose, select the valves and suck the water from the jerry can using my onboard pump...then set levers to "system use". Took some getting used to, but I like not hoisting jerry cans now. If I want to fill up from the 33 gallon tank in the back of my truck the separate hose has enough pressure to fill directly into the tank as if it was city water.

Daryll