A Virgin Australia flight headed from Los Angeles to Sydney was forced to turn around after a plumbing problem caused the bathroom to overflow. Passengers complained of an unbearable smell after liquid from bathrooms ran down the aisles and claimed that human waste had seeped into the cabin.
http://www.foxnews.com/travel/2014/11/04/unbearable-smell-from-overflowing-bathroom-forces-virgin-australia-plane-to/?intcmp=latestnews