The all-around-guy at our subdivision cleaned out the sewer in the neighborhood a few months ago. Getting rid of the accumulated dirt and garbage in the sewers is something he does every year. This year, though, he left marks on the manholes so he'll know which way everything flows to. It seems that it goes from left to right or vice-versa. I don't know which anymore.
The kids had taken interest in them and traced the arrow marks until they reached the last manhole. Last week, the kids told me that the arrow mark in front of our house is gone. I checked it out and saw that the arrow mark indeed is not visible anymore. It's obvious that our all-around-guy did not use a good marking paint for the arrow marks. He may have used just ordinary paint for it.
I would suggest to him to use a marking paint next time. Marking paints last a long time than ordinary paint. In a place where it floods easily, it is important to have the sewers cleaned and cleaned correctly. The marking paint and arrow markers will make his work easier.