In my case, it seems failure of the elbows is the issue, as in they have cracked over time. My plumber suggested replacing the entire run and cutting into the stud wall to effect the replacement. Of course this is an easier thing to do rather than trying to fish for flexible cable etc but I will put this to him as an alternative.Seems to be a long term material compatibility issue between adhesive & condensate. Nobody's fault just unfortunate, well perhaps the adhesive manufacturer. See what your plumber has to say, he may be able to suggest an alternative route.