I planned for a rather large in door plumbing system in my fort, complete with water wheels, water falls, and the ability to uhhh..... "clean" the rooms of nobles while they sleep.
The thing spanned probably 15 Z levels and everything was done in advance so any digging I did around the cannels was completed BEFORE they were filled with water to avoid those god damn "DAMP STONEZ!?!" messages.
The whole thing was supposed to be emptied by a set of pumps powered by a single water mill that was on the layer just above the plumbing. This system was connected by an ultra complicated series of axles and gears.
Just before I was ready to test it I decided to build two HUGE overflow cannels, just in case.
I think the problem problem with the system was either #1, there was too much of a load on the wheel so it didn't turn at all, or #2 the wheel was too close to the edge of the map so no water was flowing. Either way the cannel filled up almost completely before I cut off the water sources and opened the overflow channels. A while later all the water evaporated and I decided to try it again.
This time I put the water mill on the brooke to power the pumps. That of course didn't work because brookes are special tiles. Okay, fine, I'll channel some out and put it here.
Saddly the square I channeled out was the wall between the brooke and the channel, which was now rapidly back filling. I locked the area down and begain figuring out how to fix my failure. Then the messages started poping up "Urist can not reach jobsite: Dangerous terrian.
I looked back at my glorious project to see water falling down the holes I'd made for the axles.
PANIC! I walled off the entire wing of my fortress to stop the flood just in time. Glad thats over!
I remembered the water falls and the grates that covered the open air that led directly to my pipes just after water started shooting up from the ground. More panic, more constructions, more walled off fortress.
With half my fortress now flooded I set about finding a way to cut off the rivers flow. I set up some pumps and water mills and tried to make a couple of channels to pump water out of my pipes, into a resivor, and then back into the river. I was in a hurry to hook everything up so I didn't connect any gears to switches.
Long story short, by the time I abandoned, half of the underground and half of the surface were completely flooded.
Wait, was this supposed to be a thread about projects that succeeded?