If I mow a lawn full of weeds or black medic before I leave I will wash the deck off with their water hose. I do that when I run over their dog poop too. If they don't like it, I tell them to spray their yard and clean up the poop.
2013 Exmark Pioneer S 60" Ultracut (Review with pics) http://www.lawnsite.com/showthread.php?t=410996
2010 Badboy Outlaw 6100 31 KAWI
2008 Exmark Lazer Z AS 60" U/C 28 Kawi
2000 Exmark Lazer Z 60" L/C Kawi 4100 + hrs strong