In this case, I'm the plumber. I don't want to be in a position as a plumber where someone mandated that $pipeSystemX had be to used, for non-technical reasons

In this case, I'm the plumber. I don't want to be in a position as a plumber where someone mandated that $pipeSystemX had be to used, for non-technical reasons, then it breaks, and I'm 'responsible', but can't fix it. The 'fix' is to replace some or all of it, but contractually, legally, I can't touch it, but the homeowners and neighbors keep coming to ME to 'fix' things, largely because no one else even answers the phone. And turning it around, if a plumber told me "hey, I'm not allowed to replace this outdated hazardous inefficient $pipeSystemX"... yeah, I'd want to get in to some details.