If you look at real life examples of manual washing, they use tubs of water, not 800 units of water per article of clothing.
Looking at CDDAs bloody/gore/poo/giblet covered clothing, I would say you would be hard pressed to get a full load out of a bucket of water, but 1 shirt?
What this does do is more effectively tie the player to water, which is what hu-mans have traditionally have been. We do rivers and and oceans well.