There has to be some deterrent to stop people pouring a tin of paint or whatever down there. Water from here is filtered and only part treated and likely discharged into rivers or streams so not like sewerage. However these drains also pick up all the road run off including diesel, leaking oil or transmission fluid from vehicles which is much more harmful environmentally than coffee. I think a warning would suffice but where do you draw the line? Is bottled water ok? What if its carbonated? Milk ok? Coca cola?
pavement parking in almost every instance.
