The city water connection is always easier, but what if you want to fill your fresh water tank using the "manual" fill port from inside the van? Stick a funnel in there and spill water all over? Screw that.
http://morebeer.com/products/easy-siphon-38-inch.html
set a bucket or jug up on the counter and let gravity do the work!
(don't mind the towel, that was there just in case...)
This works for filling up the tank with pre-diluted sanitizer too.