One of my old coworkers lived in a whole neighborhood where the builders ran the main supply lines for every house under the living room slab, some sort of questionable plastic line (I don't remember what kind), and the whole neighborhood basically had all their main supply lines burst under their living rooms over about a two-year period.

My point is never underestimate the corners builders will cut to save like $50 or whatever even when they're building an entire house.