Originally Posted by
smoothy
How old is the house? At least we know you don't have a septic tank issue of cessfield issue.
I'd recommend having a plumber come out....snake it out to the street....and run a camera through the pipes to make sure they don't have any collapsed sections of have low spots from ground settling. If you have either of those conditions you wil lhave recurring problems until they are corrected.
Also trees anywhere near the path of the sewer line will send masses of roots that will clog up the pipes. and they can do this a surprising distance.....a camera will show any of these conditions and worth the expense for peace of mind.