Fluid

Liquids are blocks that can form pools, streams and even oceans, can flow and spread out over an area, form falls, and allow for swimming and floating.

Liquid properties
There are currently only two liquids in Minecraft: lava and water. The decorative effects of flowing water or lava add motion to a landscape and their properties enable some interesting constructions of use to the player.

This page describes the properties and behaviours that are unique to liquids, but that apply to all of them. Properties and behaviour that are particular to Water and Lava are described on their individual pages.

Milk does not count as a liquid as it can only exist as a filled bucket .. it cannot be placed as a block and is not an item on its own. Air is also not a liquid as it cannot exist as an item and does not flow.

Liquids Are Not Items
Liquids are unique as they are not available as items, they can only exist as a block in a world. Blocks of still liquid can be be picked up by using a Bucket and are then carried as filled buckets (inventory or in chests).

Liquids Flow
Another unique property is that generated or placed liquid blocks that are not confined by surrounding solid blocks will create additional liquid blocks around themselves. The resulting flow will spread out (over level ground) or create waterfalls (when near an edge). The still blocks that start a flow are called "source blocks" and the rest are flowing blocks.

Special Naming of Liquid Blocks
A still liquid block has the expected name, "water" or "lava", while the name of a flowing block will be prefixed with "flowing_", so "flowing_water".

Dripping
When particles are enabled in the game options solid blocks that have air below and liquid above will drip as a visual indication that one thin layer of ceiling blocks are all that is keeping the player dry. Dripping Lava does not cause damage or start fires. Newly revealed ceiling blocks can take several seconds to start dripping as they need to receive a block update.

Flowing Speed, Direction and Depth
Flowing liquid has a speed value in each world that governs how fast the spreading effect works. For instance Lava in the Overworld spreads much slower than Water, while in The Nether it moves much more like it. Liquid blocks in a flow are less full the further they are from their source, and render with animated lines that show their direction of flow and the reduction in level towards the edge of the spread. The direction of flow is modified by solid blocks that obstruct the flow, and by meeting flows from other sources.

Liquid Affects and Effects
Liquid flows affect the blocks they flow over or past, according to the world they are in, their properties, and the nature of the liquid. They also exert pressure on objects floating in them, carrying them along or down, and in the case of mobs, possibly trapping them.

Numerical Depth
Liquids have a depth value that is used when rendering its appearance and calculating how it flows. There are eight levels of depth, from zero to seven. The numeric value of depth is smallest for a source block (zero), rising to the maximum value of 7 for the blocks at the limit of spreading.

How Liquids Spread
Liquid spreading begins by considering the block directly below a source. If that is an air block it is changed to be a flowing_* block with a depth value of 1. The liquid will not spread sideways from a source in this situation. Flowing_* blocks with depth less than seven (7) are treated as sources in this process. If the block below is the same sort of liquid it is considered as solid.

When the block under a source is solid the 5 block area around a source is checked for air blocks a block below its level. If there are such air blocks the spreading effect will only be applied in the direction of the closest such air block by changing the first air block in that direction to flowing_* with depth one greater than the source's.

When the ground is level within 5 blocks the four blocks around the source are next to be considered. If any of the four are air blocks they are changed to flowing_water blocks with a depth value one greater than the source's. In this evaluation flowing_water blocks with depth less than seven (7) count as sources for possible further spreading, but those at depth seven are ignored.

Transparent blocks that are affected by a flow get special handling and are then treated as "air" blocks by these rules. Decorations are first either destroyed or dropped as items into the flow, according to their properties, then the block is changed to be flowing_*.

Transparent blocks that are unaffected by flows (signs, ladders, glass panes, fence posts etc.), and other water source blocks, count as solid blocks that stop, or obstruct a flow.

Note that if the "block below" or any of the "four around" are flowing_* their depth value will be adjusted according to the interaction rules later on this page. If all four surrounding blocks are solid the spreading procedure stops as there is no where for a flow to go.

Special Notes:
 * 1) blocks that were added because they were below a source block will always have depth value 1.
 * 2) blocks with the maximum depth value are the limit of spreading
 * 3) flows near a cliff edge will only spread in the direction of that edge.

Note 1 means that falling water will always reach the ground below its source

Warning: this section is based on my observations of the game in versions 1.7, .8 and .9 Bytebasher (talk) 18:50, 21 September 2015 (UTC) YMMV.

Block Updates for Liquids
There are some types of block updates particular to liquid blocks:
 * Another type block is placed into it's space
 * Liquid starts to flow in from an adjacent block
 * An established incoming flow stops

Liquid blocks are considered as "empty" so the placement of another block into it always succeeds. The destruction of the source block causes an update to all of the water blocks flowing from it. These updates ripple down the flow, increasing the depth value of each flowing block by 1 each update until the block disappears.

Note that placing a liquid into an existing source block's space fails leaving its bucket full. Placing a liquid into a flowing_* block replaces it with the source block and empties the bucket.

Generated Structures never cause block updates to adjacent liquids when they spawn. For example, a cave entrance that is created partly below water level at the edge of a body of water/lava will remain dry until one of the blocks in the opening is mined, a solid block is placed in the opening, or a liquid source block is placed that interacts with the liquid blocks in the opening.

On the other hand, liquids created as part of structure will flow immediately if not completely confined, like irrigation channels in desert villages on 1- or 2-layer super flat worlds or holes in the bottom of an ocean that open into a cave below.

Interactions Between Flows
When flows from different sources meet one another the depth of one or both will be adjusted according to these rules:
 * 1) If there is now a liquid block of the same type above a liquid set its depth level to 1
 * 2) consider the depth levels of any liquids of the same type in the four surrounding blocks - set the depth level to one more than the lowest level of the surrounding blocks found.
 * 3) If the depth level change of the previous step would increase it above the maximum for the liquid and world, then change the liquid block into air.
 * 4) the depth level of a flowing block cannot be reduced to less than 1, so source blocks cannot be created by combining flows.

Every block that has its depth level adjusted is also re-evaluated for its direction of flow.

Source Block Creation
In certain situations some liquids can create source blocks. See the pages for Water and Lava for more.

When Liquids Collide
Putting a water source next to a lava source converts the lava source to obsidian, because the water flows faster.

Flowing water contacting a lava source will also convert it to obsidian. The common knowledge is that water flowing down onto a pool of lava will convert all the lava it spreads over into obsidian, but the effect also happens when a flow of water spreading horizontally reaches a lava source before it can establish flowing lava around itself.

Flowing water that contacts flowing lava at its minimum depth (so at the maximum extent of its spread) will do nothing .. the lava will even prevent the spread of the water as if it was a transparent block without any other effect. But if the flowing lava is not at minimum depth the contact with flowing water will produce blocks of cobblestone along the boundary.

Flowing lava falling down onto water, source or flowing, converts it to stone, but this effect is difficult to observe because the faster flowing water normally "gets there first" and produces cobble or has no effect. But when lava starts flow onto an already established flow of water it will produce stone.

Gallery
Flüssigkeit Líquidos Fluides 液体 Vloeistoffen Ciecze Жидкости 液体