Plumbing codes vary between residential and commercial installations and are generally adopted at the state or local level.
It might also be the pipes are not properly supported, or plumbing joints are loose or faulty from old age, improper ...
Traditional methods of pipe fittings as well as manual repairs now represent ancient plumbing techniques. Advances in current ...
This counterintuitive bit of secret knowledge might be the result of the sheer weirdness of plumbing fittings in general.