Recently we started noticing several issues with drainage in our master bathroom/shower, that resulted in overflow into our downstairs kitchen sink. They look to both be on the same plumbing stack.
We called a couple of plumbers into review and they tried to unclog. One did a full camera inspection and found that the issue causing the blockage, which went back to the sewage line, was due to the sagging pipes under the basement foundation. They said these were not installed properly, which is causing the water to pool in the pipes (sagging area), and that overtime this build up has caused the blockage. They also said the grading was a concern.
The plumbers were surprised that this issue was occurring in a new home. The guidance I got was that the only permanent fix is structural by digging up the basement foundation and flooring under which this pipe runs (around the utility room), and replace these with straight/non-sagging pipes. This will have to be done to the outside sewer line. Otherwise the clogging will return as the sagging pipes will again start building up.
Is this true? Would hydro jetting work as an alternate to snaking (which we tried)? Or do pipes have to be replaced.