There are plenty of taps though there can be big queues at certain times of day, mainly early morning, and your feet will get muddy there, no matter how dry it is.
The real challenge lies in getting the water back to the van and then tipping it into the tank. The first problem can be overcome with one of those round water things that you can roll along. The second problem depends on the location of the tank and how high up the hole is but you either need ingenuity, strength or both.