I haven't washed/rinsed yeast for quite a few years when harvesting. Just pour the swirled up contents of the carboy into a pint canning jar. Storing under beer keeps the cell walls of the yeast in better condition than water. I'll save two pints of a yeast I don't use too often in case a jar may show an infection later.
Yeast can be frozen when combined with a glycerin solution but I haven't gone that far yet.