get the line scoped
Either the guy just screwed up, or you got a problem with the city sewers.
If their is mud in the line, he broke the line somehow.
The One sure thing to do is to hire a company to "scope the liine" with a camera and make sure for yourself that their isnt already a break that would let MUD into the pipe. This is gonna cost you about $200.
but if the guy messed up and does not want to admit it, you still have time to force him to do the job right or take him to court.!!
For all you know when he filled the hole back in he could have been careless and dropped a boulder on your pipe.
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If you find out that this isnt the problem here then you got troubles.
The only solution you got...
Install a back flow preventer in the line. I dont know wether the man cut your concrete inside your house or if he just tied into the existing line outside somewhere.
If he came into the house and left you some new concrete leading out to the basement wall the floor can be torn up and this valve can be installed. Usually everyone I have done , I have used a 5 gallon bucket
to make an access opening down to the valve for future service.
The 5 gallon bucket sounds a little cheesey and cheap. but it works fine forever and you install it flush with the floor. It has a great lid on it too.
this is probably gonna cost ya about $1000- or more
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Now this idea sounds almost silly and ridiculous, but I have seen it done by desperate people getting their finished carpeted basement flooded out every spring. (with all the neighbors raw sewage)
Nothing like finding a strang condom drying up on your wet basement floor.
if he tied onto the sewer outside, then things get really ugly....
you can dig up the front yard right by your house, I assume he installed a clean out in the yard?? yes--no??
anyway, install a 24 inch manhole down to the drain and put the back flow preventer in out there. This manhole I am talking about is just a common pvc meter pit with cast iron a lid on it. probably going to have to use a ladder to get down to check out the valve every so often, BUT IT WORKS
the people that did this in the city had a big problem untill they simply
""bit the bullet"" and went out into the yard to solve their problems
I am sorry, but you got some fun ahead of you