That’s not what it meant
I’m not sure whether this is a sign for a car wash, a private bath, or somewhere to give your pet a clean, but I think someone else needs to spend time in the dictionary corner. The word unlimited definitely doesn’t mean what this guy thinks it means, and he’s also employing the tactic of using the small print to save his butt.
I get that most people can wash their cars, their pets, or themselves in around 35 minutes, and there’s nothing wrong with limiting the amount of water your customers can use. Otherwise, you’d find yourself out of pocket pretty quickly. However, using the sneaky tactic of hoping no one reads the sign properly definitely puts this in the sneaky column.