San Francisco To Redirect Stream Of Public Urinators With Hydrophobic Walls Department of Public Works looks to Europe for idea to paint city walls with water-repellent paint in effort to combat public urination problem Pee back paint Hamburg Some walls in Hamburg, Germany pee back. Jana Kasperkevic 13 March 2015 The city of San Francisco, tired of cleaning up after those who relieve themselves in the public, wants to test walls that pee back. The San Francisco department of public works (DPW) is hoping to paint some of the city’s walls with hydrophobic (water-repellent) paint. If urinated upon, the paint...