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Difference between revisions of "v0.31:Pressure"

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{{elven}}
 
{{elven}}
  
−
There are several mechanisms at work that try to simulate '''water pressure''' in game. While on the whole amazingly accurate, there are several unexpected quirks concerning speed and displacement. Never think you are on the safe side, especially when trying to trick the game.
+
Dwarf Fortress features some pretty complex behavior in an attempt to simulate '''fluid mechanics'''. One aspect of this behavior is seen in the form of '''pressure'''. The basic idea here is quite simple, '''{{l|flow|fluids}}''' such as '''{{l|water}}''' and in some cases '''{{l|magma}}''' can become pressurized which can result in them being pushed back up into other areas by the weight of the fluid.  
  
−
A [http://www.bay12games.com/forum/index.php?topic=32453.0 technical explanation by Kanddak] from the Bay12 Forum outlines in detail what is known of the in-game fluid mechanics from player testing.
+
=A demonstration of pressure using U-Bends=
 +
a U-Bend is a channel that digs down, and curves back up. With '''pressure''' a {{l|flow|fluid}} will be pushed up the other side of the u-bend in an attempt to equalize the pressure. By understanding how pressure works in a u-bend you should be able to adapt this knowledge to use fluids in any configuration you desire without any unexpected surprises that could make life in your fortress more '''{{l|fun}}''' than anticipated. '''{{l|water}}''' and '''{{l|magma}}''' both behave very differently with regards to pressure, so read carefully.
  
−
==Hydrostatic water pressure==
+
==Water in a U-Bend==
−
Dwarf Fortress attempts to replicate [http://en.wikipedia.org/wiki/Fluid_statics#Pressure_in_fluids_at_rest hydrostatic water pressure].
+
The following three diagrams demonstrate different ways water might behave in a u-bend. In the first example (Diagram A), we have water taken directly from a river used to fill a u-bend. In this case, because the river is free to flow out the edge of the map the water never fully pressurizes which results in the water stopping one level below the actual level of the river itself. This behavior applies to water taken from any infinite water source.
  
−
This is probably one of the most prominent components, as Toady discussed it at length in an interview with [http://www.gamasutra.com/view/feature/3549/interview_the_making_of_dwarf_.php?page=10 gamasutra].
+
In the next example (Diagram B), a '''dam''' has been placed preventing the river from flowing off the edge of the map. Because of this, the water soon becomes fully pressurized and quickly fills up the remaining level of the u-bend. Use caution when placing a dam on your river. {{verify}}
  
−
In layman's terms, if you have a body of water that is higher than an open space below it (such as a tall tower full of water and a hose from it, or a {{l|lake}} over a mine), and an open route between them, then the water at the lowest {{|z-level}} will be 'pressed' by the weight of the water above it.  
+
The final example (Diagram C), demonstrates how a '''screw pump''' pressurizes water up to the level of the pump. In this case the water is actually being taken to one level above the river because it is being pressurized by the pump.  
  
−
As a simple model, think of a pipe shaped like a "J". If you pour water in the taller end of the pipe, it will come "up" out of the lower end until the water levels on both sides are equal. If you put your thumb over the lower end and fill the taller end, then release your thumb, the water will move with remarkable speed, and water will continue to come "up" out that lower end until all the water in the taller part is at the same level as the lower part.  This is one part of Dwarf Fortress "water pressure" -  that if the source is higher, water can come up {{l|stair|stairs}}, up {{l|ramp|ramps}}, and over {{l|channel|channels}}, and will continue flowing until it runs out of space or runs out of water above it.
+
With these three simple examples, you should be ready to go build your enormous plumbing masterpiece, and be relatively safe from any unanticipated flooding. If you plan to work with {{l|magma}} as well however, you should read further.
  
−
Note that DF water pressure does not ''exactly'' match natural hydrostatic water pressure - it fills to a {{l|z-level|z-level}} ''one level lower'' than the source.  (This is for reasons of CPU time-saving, as stated by [[Toady]]; the game stops not when all ends of the system are on the same level, but when the far levels are one-lower than the source.) The above behavior does only apply to finite water sources like murky pools, artificially created reservoirs and any body of water connected to an infinite water source only diagonally. More to the point, it applies always, but is in many cases not the final mechanism causing equilibrium.
+
    Diagram A    Diagram B      Diagram C
 +
    River        Dammed River  Screw Pump
 +
    (side view)   (side view)    (side view)<br />
 +
    ▒<font color="blue">≈≈≈</font>▒        ▒<font color="blue">≈≈≈</font>▒<font color="blue">≈≈≈</font>▒        %%<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒
 +
    ▒▒▒<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒    ▒▒▒<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒    ▒<font color="blue">≈≈≈</font>▒▒<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒
 +
      ▒<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒      ▒<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒    ▒▒▒▒▒▒<font color="blue">≈</font>▒<font color="blue">≈≈≈</font>▒
 +
      ▒<font color="blue">≈≈≈≈≈</font>▒      ▒<font color="blue">≈≈≈≈≈</font>▒          ▒<font color="blue">≈≈≈≈≈</font>▒
 +
      ▒▒▒▒▒▒▒      ▒▒▒▒▒▒▒          ▒▒▒▒▒▒▒
  
−
== Pressure from infinite water sources ==
+
==Magma in a U-bends==
−
Different from the above, a river that pushes water into a tunnel system will fill it up to the z-level of the river itself, but not higher (again, unless only connected by diagonal flow, see below).
+
'''{{l|Magma}}''' behaves very differently from {{l|water}} because it will not normally retain any pressure. In our first magma example (Diagram A) we show how this works by creating a short u-bend and connecting it up to a magma pipe. because {{l|magma}} is not a pressurized fluid, it simply fills the lowest point and makes no further attempt to go back up.
  
−
When the water source is a {{l|river}} which is allowed to drain off the edge of the map, the final Z-level will never fill - however, if a {{l|dam|dam}} prevents the river from draining, it will continue to fill up to its own Z-level.
+
Do not however make the mistake of thinking that {{l|magma}} can never be pressurized. In the second diagram (Diagram B) we see how with the addition of a single screw pump, the entire situation changes dramatically. The screw pump is pressurizing the magma so that it will now fill the area back up to the level of the pump. Accidentally flooding your fortress with {{l|magma} is considerably more {{l|fun}} than a flood of {{l|water}}
  
−
== Other/Missing mechanisms==
+
    Diagram A      Diagram B
−
Dwarf Fortress does not model surface friction nor air pressure, so the water will not slow in transit nor will 'trapped air bubbles' form. Unless pumped, magma does not have pressure unless it is pressurized with a {{l|pump}} (it cannot flow up, and doesn't appear to move at greater speeds).
+
    Magma Pipe    Screw Pump
 +
    Side View      Side View<br />
 +
    ▒<font color="red">≈≈≈</font>▒          %%<font color="red">≈</font>▒<font color="red">≈≈≈</font>▒
 +
    ▒<font color="red">≈≈≈</font>▒      ▒<font color="red">≈≈≈</font>▒▒<font color="red">≈</font>▒<font color="red">≈≈≈</font>▒
 +
    ▒<font color="red">≈≈≈</font>▒      ▒<font color="red">≈≈≈</font>▒▒<font color="red">≈</font>▒<font color="red">≈≈≈</font>▒
 +
    ▒<font color="red">≈≈≈≈≈</font>▒    ▒<font color="red">≈≈≈</font>▒▒<font color="red">≈≈≈≈≈</font>▒
 +
    ▒<font color="red">≈≈≈</font>▒▒▒    ▒<font color="red">≈≈≈</font>▒▒▒▒▒▒▒▒
  
−
As can be expected, if water is continuously pushed into a room, either by an unlimited water source like a river or by means of a {{l|pump}}, the water will not stop when the room is filled, but search for an outlet, even on higher z-levels. If there is an outlet, but it can not take all the water coming in, the water will look for further outlets.  
+
==Waterfalls==
 +
Waterfalls are of special concern. When drawing water from a waterfall it is important to understand that this water may be pressurized up to the highest point of the waterfall. So that if you tap into a natural waterfall at the low side you could very easily flood your entire fortress very quickly. {{verify}}
 +
:*Note: in the current version there have been reports that waterfalls may not "fall". They instead continue flowing at their original level and fly out into open air defying gravity. {{verify}}{{version|0.31.02}}
  
−
It's possible for dwarf-built {{l|pump|pumps}} to pick liquid up and lift it higher, possibly back to the source and thus creating a closed cycle. Beware that operating pumps obey the same pressure rules as infinite water sources, capable of pushing both water '''and''' magma down through tunnels and back up to the original Z-level of the pump's output tile.
+
=Neutralizing Pressure=
  
−
== Dangers ==
+
==Diagonal Flow==
−
It is easy to flood your fortress accidentally by not accounting for water pressure. For example:
+
Diagonal {{l|flow|flowing}} fluids create a unique behavior which neutralizes all '''pressure'''. By forcing fluids through a diagonal connection you can neutralize all pressure quite easily. Here is a top-down diagram of this effect.
−
* It is safe to dig out a {{l|cistern}} one level below a murky pool, and to channel above a few tiles of the {{l|cistern}} so that your dwarves can get water from it without having to go outside.
 
−
* It is safe to refill a murky pool with water from a pump or brook/river/etc on the same level.
 
−
* It is not safe to do both to the same pool! The water from the pump/brook/river/whatever will fill the pool to 7/7, and will then pressurize the water in the {{l|cistern}}, which will then flow up out of your channels and flood your fort.
 
−
 
 
−
===Waterfalls===
 
−
Waterfalls are of special concern.  If you tap river section ''downstream'' from a waterfall, the water will be under additional pressure as it is coming from above the river's surface. It is absolutely critical to reduce the pressure in such a system if you do not wish flooding, the easiest way being diverting the water diagonally - although if used solely for a complex drowning trap or other purpose, flooding may be desirable.{{verify}}
 
−
 
 
−
== Mitigating dangers ==
 
−
=====Diagonal Flow=====
 
−
Obviously the game treats water connected only by a diagonal tile as ''not'' connected in terms of "pressure" but ''only'' in terms of "diffusion". A common adaption of this behaviour is feeding water through a diagonal tile "to take the pressure out": 
 
−
 
 
−
Pressure cannot push water through diagonal gaps between tiles - instead, it will merely flow through if the water level on the other side is low enough.
 
  
 
  '''Top View'''<br />  
 
  '''Top View'''<br />  
−
                 ######
+
                 ▒▒▒▒▒▒
−
         #########<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font>########
+
         ▒▒▒▒▒▒▒▒▒<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font>▒▒▒▒▒▒▒▒
−
   <font color="blue">'''Direction->'''</font> <font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font>#<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font> <font color="#2FB6FF">-></font>
+
   <font color="blue">'''Direction->'''</font> <font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font>▒<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font> <font color="#2FB6FF">-></font>
−
   <font color="blue">'''  of    ->''' </font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font>#<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font> <font color="#2FB6FF">-></font>
+
   <font color="blue">'''  of    ->''' </font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font>▒<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font> <font color="#2FB6FF">-></font>
−
   <font color="blue">'''  Flow  ->'''</font> <font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font>#<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font> <font color="#2FB6FF">-></font>
+
   <font color="blue">'''  Flow  ->'''</font> <font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font><font color="blue">≈</font>▒<font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font><font color="#2FB6FF">≈</font> <font color="#2FB6FF">-></font>
−
         ###########<font color="#2FB6FF">≈</font>#########
+
         ▒▒▒▒▒▒▒▒▒▒▒<font color="#2FB6FF">≈</font>▒▒▒▒▒▒▒▒▒
−
                   ###<br />
+
                   ▒▒▒<br />
−
   # = wall, constructed or undug
+
   ▒ = wall, constructed or undug
 
   <font color="blue">≈</font> = pressurized water
 
   <font color="blue">≈</font> = pressurized water
 
   <font color="#2FB6FF">≈</font> = neutral/normal water pressure
 
   <font color="#2FB6FF">≈</font> = neutral/normal water pressure
Line 58: Line 62:
 
This does not work on a vertical basis - water only travels vertically to a different z-level, never diagonally.   
 
This does not work on a vertical basis - water only travels vertically to a different z-level, never diagonally.   
  
−
A result of this is that a tunnel system that spans several z-levels, but is connected to a river only by a diagonal tile, will fill only to one z-level lower than the river, but if an orthogonal connection is created, it will fill up another level.  
+
If you wish to maintain the rate of '''{{l|flow}}''' after de-pressurizing, it's recommended that you have more diagonals than water tiles - that is, if the source is 3-tiles wide, you may wish 4 or more diagonal passages.
  
−
If you wish to maintain the rate of flow after de-pressurizing, it's recommended that you have more diagonals than water tiles - that is, if the source is 3-tiles wide, you may wish 4 or more diagonal passages.
+
==Pumps==
−
 
 
−
=====Hatches=====
 
−
{{l|Hatch|Hatch}}es can be placed over {{l|channel|channels}}, {{l|stair|stairs}}, {{l|ramp|ramps}} etc to prevent {{l|water}} moving vertically but still allow the tile to be used, even as a water source (and possibly still for fishing too).
 
−
 
 
−
=====Pumps=====
 
 
Water pressure does not propagate through pumps, so it is possible to fill a pool using a screw pump without it having the same pressure as its source. Of course, there is a downside - you still have to run the pumps and due to the source water's pressure, the pump must be {{l|power|powered}} instead of {{l|pump operator|run by a dwarf}}, as the tile the dwarf needs to stand on is filled by water. Furthermore, the pump will likely need to be powered from above or below (as water would simply flow around a gear or axle placed next to the pump), though creative setups are still possible by using additional screw pumps to transmit power.
 
Water pressure does not propagate through pumps, so it is possible to fill a pool using a screw pump without it having the same pressure as its source. Of course, there is a downside - you still have to run the pumps and due to the source water's pressure, the pump must be {{l|power|powered}} instead of {{l|pump operator|run by a dwarf}}, as the tile the dwarf needs to stand on is filled by water. Furthermore, the pump will likely need to be powered from above or below (as water would simply flow around a gear or axle placed next to the pump), though creative setups are still possible by using additional screw pumps to transmit power.
  
−
Your vertical {{l|axle|axles}} or gear assemblies need to be placed above the unwalkable tile of the pump, and there must not be a channel over the walkable pump tile. (Water can only flow straight upward, not up and to the side at the same time.) Multiple adjacent pumps will also [[40d:Power#Power transfer|transfer power]] between themselves automatically.
+
Your vertical axels or gear assemblies need to be placed above the solid tile of the pump, and there must not be a channel over the walkable pump tile. (Water can only flow straight upward, not up and to the side at the same time.) Multiple adjacent pumps will also transfer '''power''' between themselves automatically.
  
 
  Side view
 
  Side view
 
                        
 
                        
 
     Power  Water      Key
 
     Power  Water      Key
−
       ↓    ↓↓↓↓↓      # = Normal wall
+
       ↓    ↓↓↓↓↓      ▒ = Normal wall
−
  ######<font color="brown">║</font>###<font color="blue">#</font><font color="blue"><b>≈≈≈≈≈</b></font>      <font color="blue">#</font> = Wall that pressurised water would flow into if it were to be dug out
+
  ▒▒▒▒▒▒<font color="brown">║</font>▒▒▒<font color="blue">▒</font><font color="blue"><b>≈≈≈≈≈</b></font>      <font color="blue">▒</font> = Wall that pressurised water would flow into if it were to be dug out
−
  ######<font color="brown">║</font>####<font color="blue">#</font><font color="blue"><b>≈≈≈≈</b></font>      <font color="#2FB6FF">≈</font> = Regular water
+
  ▒▒▒▒▒▒<font color="brown">║</font>▒▒▒▒<font color="blue">▒</font><font color="blue"><b>≈≈≈≈</b></font>      <font color="#2FB6FF">≈</font> = Regular water
−
  _ ___#<font color="brown">║</font><font color="blue">#######</font><font color="blue"><b>≈≈</b></font>      <font color="blue"><b>≈</b></font> = Pressurised water
+
  _ ___▒<font color="brown">║</font><font color="blue">▒▒▒▒▒▒▒</font><font color="blue"><b>≈≈</b></font>      <font color="blue"><b>≈</b></font> = Pressurised water
−
  #<font color="#2FB6FF">≈≈≈≈≈</font><font color="green"><b>%%</b></font><font color="blue"><b>≈≈≈≈≈≈≈≈</b></font>      <font color="green"><b>%%</b></font> = Pump
+
  ▒<font color="#2FB6FF">≈≈≈≈≈</font><font color="red"><b>%%</b></font><font color="blue"><b>≈≈≈≈≈≈≈≈</b></font>      <font color="red"><b>%%</b></font> = Pump
−
  #######<font color="blue">#</font><font color="blue"><b>≈</b></font><font color="blue">#######</font>      <font color="brown">║</font> = Axle
+
  ▒▒▒▒▒▒▒<font color="blue">▒</font><font color="blue"><b>≈</b></font><font color="blue">▒▒▒▒▒▒▒</font>      <font color="brown">║</font> = Axle
−
  ########<font color="blue">#</font>#######     _ = Floor
+
  ▒▒▒▒▒▒▒▒<font color="blue">#</font>▒▒▒▒▒▒▒     _ = Floor
  
 
Do note that the water output from the screw pump '''will''' be pressurized according to the "infinite water source" behavior, but said pressure will be independent of the source and can be subsequently 'reset' by additional pumps or diagonal gaps.
 
Do note that the water output from the screw pump '''will''' be pressurized according to the "infinite water source" behavior, but said pressure will be independent of the source and can be subsequently 'reset' by additional pumps or diagonal gaps.
  
−
== Overall behavior ==
+
==Hatches==
−
 
+
{{l|Hatch|Hatch}}es can be placed over {{l|channel|channels}}, {{l|stair|stairs}}, {{l|ramp|ramps}} etc to prevent {{l|water}} moving vertically but will still allow the tile to be used, even as a water source (and possibly still for fishing too).
−
* If a tile contains water which is floating on top of another tile of 7/7 water (and apparently only if there is no water above it{{verify}}), the water in the upper Z-level will be pushed downward and moved to the nearest orthogonal (not diagonal) tile on the lowest available Z-level, up to the Z-level just below the top. Each tile of liquid performs this check once every few steps. This type of pressure applies only to water, and is what causes large bodies of water multiple Z-levels deep to rapidly drain when opened.
 
−
* If a liquid source (river/brook source, underground river waterfall tile, map edge, or [[40d:screw pump|screw pump]] output) attempts to create liquid in its output tile but cannot due to it being full already, the liquid will be created in the nearest orthogonal (not diagonal) tile on the lowest available Z-level, up to the ''same'' Z-level as the source. This applies to both water and magma, and can be observed by damming a river.
 
−
* Liquids adjacent (both orthogonally and diagonally) to non-full tiles will flow into them and average their depths, pushing lightweight objects and creating flow (which will power [[40d:water wheel|water wheel]]s) if the depth difference was 2 or more.
 
−
 
 
−
See [http://www.gamasutra.com/view/feature/3549/interview_the_making_of_dwarf_.php?page=9] and [http://www.gamasutra.com/view/feature/3549/interview_the_making_of_dwarf_.php?page=10] for more info from Toady.
 
−
 
 
−
===Movies of pressure experiments===
 
−
* [http://mkv25.net/dfma/movie-283-grandwaterpressureexperiment] - Showing that pumps output 0-pressure water even from a high-pressure source, that water will not flow up and to the side at the same time (has to flow straight up), and a few other things
 
−
* [http://mkv25.net/dfma/movie-284-firstwaterpressureexperimentreproduced] - Showing that pressure is not transmitted through non-7/7 tiles.
 
−
* [http://mkv25.net/dfma/movie-285-waterpressureinriverexperiment] - Pump turned into infinite water generator, but still provided useful information on how overpressure causes upward flooding. The infinite water generation behavior has since been fixed.
 
−
* [http://mkv25.net/dfma/movie-288-waterpressureexperiment4] - Uses three pumps connected to different tunnel layouts to test a few of these rules: One tunnel has three accessible z-levels. The second tunnel has one accessible z level and periodic shafts up. The third has only one accessible z level with no shafts. The bottom level of all three filled first, and the shafts did not fill until the bottom was filled. The second level of the three-high tunnel did not begin filling until the first was full. They did not all fill the bottom at once, but this is believed to be due to the order in which their pumps are placed on the river.
 
  
 
== See Also==
 
== See Also==
Line 102: Line 90:
  
 
{{l|Water FAQ}}
 
{{l|Water FAQ}}
−
 
 
[[Category:Physics]]
 
[[Category:Physics]]

Revision as of 01:52, 12 April 2010

v50.14 · v0.47 · v0.34 · v0.31.25 · v0.28 · v0.23
This article is about an older version of DF.

Template:Elven

Dwarf Fortress features some pretty complex behavior in an attempt to simulate fluid mechanics. One aspect of this behavior is seen in the form of pressure. The basic idea here is quite simple, Template:L such as Template:L and in some cases Template:L can become pressurized which can result in them being pushed back up into other areas by the weight of the fluid.

A demonstration of pressure using U-Bends

a U-Bend is a channel that digs down, and curves back up. With pressure a Template:L will be pushed up the other side of the u-bend in an attempt to equalize the pressure. By understanding how pressure works in a u-bend you should be able to adapt this knowledge to use fluids in any configuration you desire without any unexpected surprises that could make life in your fortress more Template:L than anticipated. Template:L and Template:L both behave very differently with regards to pressure, so read carefully.

Water in a U-Bend

The following three diagrams demonstrate different ways water might behave in a u-bend. In the first example (Diagram A), we have water taken directly from a river used to fill a u-bend. In this case, because the river is free to flow out the edge of the map the water never fully pressurizes which results in the water stopping one level below the actual level of the river itself. This behavior applies to water taken from any infinite water source.

In the next example (Diagram B), a dam has been placed preventing the river from flowing off the edge of the map. Because of this, the water soon becomes fully pressurized and quickly fills up the remaining level of the u-bend. Use caution when placing a dam on your river. [Verify]

The final example (Diagram C), demonstrates how a screw pump pressurizes water up to the level of the pump. In this case the water is actually being taken to one level above the river because it is being pressurized by the pump.

With these three simple examples, you should be ready to go build your enormous plumbing masterpiece, and be relatively safe from any unanticipated flooding. If you plan to work with Template:L as well however, you should read further. 

    Diagram A     Diagram B      Diagram C
    River         Dammed River   Screw Pump
    (side view)   (side view)    (side view)

    ▒≈≈≈▒         ▒≈≈≈▒≈≈≈▒         %%≈▒≈≈≈▒
    ▒▒▒≈▒≈≈≈▒     ▒▒▒≈▒≈≈≈▒     ▒≈≈≈▒▒≈▒≈≈≈▒
      ▒≈▒≈≈≈▒       ▒≈▒≈≈≈▒     ▒▒▒▒▒▒≈▒≈≈≈▒
      ▒≈≈≈≈≈▒       ▒≈≈≈≈≈▒          ▒≈≈≈≈≈▒
      ▒▒▒▒▒▒▒       ▒▒▒▒▒▒▒          ▒▒▒▒▒▒▒

Magma in a U-bends

Template:L behaves very differently from Template:L because it will not normally retain any pressure. In our first magma example (Diagram A) we show how this works by creating a short u-bend and connecting it up to a magma pipe. because Template:L is not a pressurized fluid, it simply fills the lowest point and makes no further attempt to go back up.

Do not however make the mistake of thinking that Template:L can never be pressurized. In the second diagram (Diagram B) we see how with the addition of a single screw pump, the entire situation changes dramatically. The screw pump is pressurizing the magma so that it will now fill the area back up to the level of the pump. Accidentally flooding your fortress with {{l|magma} is considerably more Template:L than a flood of Template:L 

    Diagram A      Diagram B
    Magma Pipe     Screw Pump
    Side View      Side View

   ▒≈≈≈▒           %%≈▒≈≈≈▒
   ▒≈≈≈▒       ▒≈≈≈▒▒≈▒≈≈≈▒
   ▒≈≈≈▒       ▒≈≈≈▒▒≈▒≈≈≈▒
   ▒≈≈≈≈≈▒     ▒≈≈≈▒▒≈≈≈≈≈▒
   ▒≈≈≈▒▒▒     ▒≈≈≈▒▒▒▒▒▒▒▒

Waterfalls

Waterfalls are of special concern. When drawing water from a waterfall it is important to understand that this water may be pressurized up to the highest point of the waterfall. So that if you tap into a natural waterfall at the low side you could very easily flood your entire fortress very quickly. [Verify]

  • Note: in the current version there have been reports that waterfalls may not "fall". They instead continue flowing at their original level and fly out into open air defying gravity. [Verify]v0.31.02

Neutralizing Pressure

Diagonal Flow

Diagonal Template:L fluids create a unique behavior which neutralizes all pressure. By forcing fluids through a diagonal connection you can neutralize all pressure quite easily. Here is a top-down diagram of this effect. 

Top View
 
                ▒▒▒▒▒▒
        ▒▒▒▒▒▒▒▒▒≈≈≈≈▒▒▒▒▒▒▒▒
 Direction-> ≈≈≈≈▒≈≈≈≈≈≈ ->
    of    -> ≈≈≈≈≈▒≈≈≈≈≈ ->
   Flow   -> ≈≈≈≈≈≈▒≈≈≈≈ ->
        ▒▒▒▒▒▒▒▒▒▒▒≈▒▒▒▒▒▒▒▒▒
                  ▒▒▒

 ▒ = wall, constructed or undug
 ≈ = pressurized water
 ≈ = neutral/normal water pressure

This does not work on a vertical basis - water only travels vertically to a different z-level, never diagonally.

If you wish to maintain the rate of Template:L after de-pressurizing, it's recommended that you have more diagonals than water tiles - that is, if the source is 3-tiles wide, you may wish 4 or more diagonal passages.

Pumps

Water pressure does not propagate through pumps, so it is possible to fill a pool using a screw pump without it having the same pressure as its source. Of course, there is a downside - you still have to run the pumps and due to the source water's pressure, the pump must be Template:L instead of Template:L, as the tile the dwarf needs to stand on is filled by water. Furthermore, the pump will likely need to be powered from above or below (as water would simply flow around a gear or axle placed next to the pump), though creative setups are still possible by using additional screw pumps to transmit power.

Your vertical axels or gear assemblies need to be placed above the solid tile of the pump, and there must not be a channel over the walkable pump tile. (Water can only flow straight upward, not up and to the side at the same time.) Multiple adjacent pumps will also transfer power between themselves automatically. 

Side view
                      
    Power  Water      Key
      ↓    ↓↓↓↓↓      ▒ = Normal wall
▒▒▒▒▒▒║▒▒▒▒≈≈≈≈≈      ▒ = Wall that pressurised water would flow into if it were to be dug out
▒▒▒▒▒▒║▒▒▒▒▒≈≈≈≈      ≈ = Regular water
_ ___▒║▒▒▒▒▒▒▒≈≈      ≈ = Pressurised water
▒≈≈≈≈≈%%≈≈≈≈≈≈≈≈      %% = Pump
▒▒▒▒▒▒▒▒≈▒▒▒▒▒▒▒      ║ = Axle
▒▒▒▒▒▒▒▒#▒▒▒▒▒▒▒      _ = Floor

Do note that the water output from the screw pump will be pressurized according to the "infinite water source" behavior, but said pressure will be independent of the source and can be subsequently 'reset' by additional pumps or diagonal gaps.

Hatches

Template:Les can be placed over Template:L, Template:L, Template:L etc to prevent Template:L moving vertically but will still allow the tile to be used, even as a water source (and possibly still for fishing too).

See Also

Template:L

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