Hi Erica,
There are some convenient accessories that allow you to wash your tank
out from outside without dragging a hose inside.
If it is a straight shot from the dump pipe into the tank, Valterra makes
an elbow for your dump hose that incorporates a washout hose fitting and
jet that aims a jet of water into the tank through the dump pipe and
valve. If there is an angle, their Master Blaster tank wand has a jet set
at a right angle that can be stuck up into the pipe to shoot water back
into the tank.
Don't forget the antifreeze if you leave those 2 bowls of water in the
tank over the winter, unless you live pretty far south.
Al