So, I've never really cared for the traditional pump stacking method, as it doesn't fit symmetrically with my odd-numbered fortress layout (5x5 room base, usually). So I came up with this:
Floorplan sans pump:
OOOOOOO
O+++++O
O+++++O
O^+_++O
OO++++O
O++v++O
OOOOOOO
With Pump:
OOOOOOO
O+++++O
O+++++O
O^+%++O
OO+%++O
O++v++O
OOOOOOO
^ is an up ramp
v is a down ramp
O is wall
+ is floor
_ is channel
Rotate ninety degrees clockwise for each level above this.
I haven't gotten it wet yet, as it's the spine of a thirty-story megaproject. But I'm pretty confident that it'll work, if less efficiently than a standard pumpstack. This method appealed to me because I'm trying to leave as much of the natural rock in place as possible: The ramp system lets me dig all the way to the bottom of the map, and provides access to construct the pumps without knocking out any of the stack's walls.
The one sticking point is probably going to be my power system. I currently plan to power it using a variation on the dwarven perpetual motion machine, using an open loop instead of a closed system. Water at the bottom of my lake flows through diagonal openings to kill pressure, then past a series of waterwheels, then to a pump that pumps it into the pump stack, providing both water and power to the system. Of course, this will make it very problematic to shut off once it's going. I think it would actually be impossible to start a second time, since the pumps at the bottom would need to be dwarf-started, and the water would be trying to move into the already-filled pump stack. That doesn't work, does it?
A diagram of the power feed:
[code]
_
%
OOO%OOO
O++|++O
O++|++O
_%%==*==%%_
O++|++O
O++|++O
OOO%OOO
%
_
[code]
I'm waffling a bit about the level below this one. I can either put in pressurized feed lines to the pump stack, to guarantee sufficient flow, or drain lines, to make sure I can stop and start it. It's possible I could manage both, I suppose. What would you do?[/code]