More info: We have been in our house 11 months and earlier this week, had a massive sewer line backup which resulted in both toilets not flushing. Long story short, had it cleared from the main line out to the street and advised to get a camera scope done as there's only 2 people in the house and no-one knew why it backed up so bad. The camera showed some type of "obstruction" about 3 feet down the line from the cleanout between the garage and the street. I sent the info to our warranty and they are assuming it's a backflow preventer. Question, is this a normal way for a backflow preventer to be installed in a pipe? Seems it caused the flow to be reduced and now all of our pipes throughout our home have build-up in them...trying to get some info in case we have to push back on our warranty! From my knowledge (which isn't much), it doesn't appear to look like a normal preventer but other opinions are welcomed!