My name is ***** ***** I am sorry for your wait.
This is likely a piping snafu where someone tapped off a service line instead of the main.
If the basement/crawl is open then it will be an easy fix....allow $300
This is contingent on piping being avail.
It is pretty obvious they have ran a line to the kitchen from a incorrect takeoff.
I still stand by reason and cost..BUT...it is based on piping being accessible to correct the issue. If the piping is boarded or finished in it will get costly fast.