Treated Wood is very cheap and can be used for Water Pipes. However the major downside I find is its flammability excluding its use anywhere near Burning Boxes, including Distilled Water supply for Boilers of course.
With the vast reserves of (Anthracite) Coal, Lignite and even Peat, I think none of these can have a shortage before late-game. Thus I tend to use Coal Coke for its better burning value, while Lignite serves as a source of Germanium if you want to go for higher tier Solar Panels.