Hmm... It's odd that another mod that allows you to lay pipes underground doesn't limit them to a depth of 2-3 levels (down to sea level), but allows the same placement rules as on the surface. Is this limitation unique to the current mod, or is there some other gameplay mechanic at play?

Hey! Yeah, that's almost certainly Cheat++ you're thinking of — it's got a similar underground-pipes thing built in, but since it's a cheat mod it just lets you bury them as deep as you want.

With this one I honestly wanted to keep things close to vanilla, so I kept the depth shallow on purpose — felt more in the spirit of the base game than digging tunnels to the center of the earth (and the game itself won't let a pipe go below sea level anyway, so going super deep isn't really a thing).

So if you're after unlimited depth, Cheat++ has you covered — but if you'd rather keep that vanilla balance, that's exactly what I was going for here.