Brian 'The Boz' Bosworth Sued Over Poop System Disaster in Mansion from 'The OC'

Famed NFL draft bust-turned-actor Brian "The Boz" Bosworth is at the root of a massive poop problem ... inside a giant mansion featured on "The OC" -- this according to a new lawsuit filed by his former tenant.

Boz used to own the giant Malibu mansion -- featured prominently on Season 1 of everyone's favorite TV show (below) -- and he rented it out to a company called Grasshopper House LLC in 2006, which currently runs the famous Passages rehab center down block. Boz has since sold the house.

But things didn't go so well between Boz and Grasshopper -- which claims the property's septic tank went to s*** between 2008-2009 ... and GH was forced to sink over $50,000 of its own money into fixing the problem.

In addition to its septic tank money, GH is also suing for a huge chunk of rent it claims it wasted while the septic system was busted -- $150,000. GH claims it lost the use of several rooms due to the poo SNAFU.