The point was that even a wholly unqualified person who is likely to do more harm than good in the attempt would be expected to do so, not that you would ask them for help.

Why not ask a person who has spent years learning about plumbing, materials, health requirements, for help instead? They usually come with practical experience in the installation and maintenance and also know the most cost efficient way to do all this. In exchange you could provide them monetary compensation for their superior knowledge, skill and experience on the subject.