Setting up RV to use water pump instead of Park Supply

Perhaps I'm not understanding what you want to accomplish but yes, you can fill your water tank and just use the water pump to draw your water needs. This is done all the time why staying at dry campgrounds or boondocking. No need to do anything special. A tank of water will last a long time, especially if you conserve and don't let the water run needlessly.

It doesn't take a lot of effort to fill the tank. :)