Spilled Lots of Dish Soap into Gray Water Tank - An Issue?

When I need to give my black and gray tanks a good cleaning this is what I do. I add some liquid soap(about the same amount I would use to do a large load of dishes) to both tanks then put about 10 Gallons of water in both of them. Then I drive to our next campground then I dump them. What can it hurt it cleans them like a washing machine cleans your cloths in my opinion.