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I currently have two large ponds filled with water to depth 7 that I need to get drained. Because I didn't think very hard about how liquid flow works, the out pipe on the one is one tile wide, controlled by a floodgate, and it's draining really slowly. The other one doesn't have an out pipe yet, but I had pretty much the same plan.

I'm thinking there must be a more efficient way to do this. Do I simply need a wider out-pipe? If so, can I connect multiple floodgates to one lever? (I'm favoring mechanical simplicity here.) Or is there an even better way? Assume that my pond isn't actually flooded, so a good pre-flooding setup will work too.

Here's a picture of the more interesting pond:

My death pond

This one is directly below my trap-filled maze, hence all the ballista arrows, blood and corpses. I flooded it for a long siege which just finished up. The larger body of water to the north is the river, with its floodgate closed. The out pipe goes off to the west and ends at a floodgate (open) and a fortification (flooded). The tubes are weirdly shaped because that red ore is delicious hematite. And yes, my pond of death is adjacent to my bedroom area.

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    The sound of intruders and enemies dying screaming drowning deaths is a soothing lullaby for dwarven babies.
    – Shadur
    Oct 30, 2012 at 11:39

2 Answers 2

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A wider pipe will cause it to drain faster, as will an altitude drop as Martin Sojka suggests. Not sure which will be more effective; if you do both it should drain pretty fast. I know when I was building a waterfall in my dining room, it tended to back up sometimes when the drainage to the caverns was only 1 square.

You can connect any number of things to a single lever or pressure plate. There is no limit (well, no meaningful limit, probably if you try to connect more than 65k things it gets confused). So feel free to go wild with that.

Since you're fiddling with drainage systems, I'll give you another bit of advice for free: especially if you build a wide drainage pipe, put in some vertical bars blocking the outflow, with some convenient stairs up right in front of them. Otherwise, Urist McMason will decide that he just absolutely needs to use a rock left behind when you were digging out the sewers, and if there's any way he can find to get there, he'll go charging down to grab it and get washed away by the current. Give him something to hit before he gets washed entirely off. I had this happen to me with my waterfall as well; the poor guy got washed out the sewers, down the 6 z-level drop to the floor of the first cavern.

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Drain the ponds to some place lower than their lowest point. The water pressure will make sure they'll empty into them almost instantly. If you're worried about the pressure overflowing and pushing the water back up, make a simple de-pressurizer somewhere on the pipe, like this:

                           ####################
                           ############         <- pressurized water in
depressurized water out <-             ########
                           ####################

(Version 0.31.25)

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  • The depressurizer (as drawn) will unfortunately also tend to restrict the flow rather heavily. Not sure if that's a problem.
    – Paul Z
    Oct 19, 2011 at 21:45
  • @Paul Z: It restricts the flow to the same rate as a level 7 water to the side of an empty space would have at the beginning, and more as the depressurized size starts to fill up. In general, it's fast enough to move about a cell's worth of water every two to three frames from the pressurized side until the other one fills up. If that's too slow, use a wider channel. If that's still too slow you can use a pump, though it has to be created in a special way as detailed on the wiki page about neutralizing water pressure.
    – Martin Sojka
    Oct 21, 2011 at 7:29

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