A multiblock tank is a sealed, hollow box that you build from individual tank blocks. The easiest way to learn it is to copy the small 3×3×3 example below first, get it to form, and only then build larger tanks.

Do not fill the inside with water blocks. The inside of the structure must stay empty air. The tank stores fluid in the machine itself.

This is different from the single-block Water Tank, which stores 100 L on its own. Both accept any registered liquid, including water and lava, one liquid at a time. Empty a tank completely before changing liquids; buckets and pipes never mix them. Pumps and Boiler Engines still require water.

This is an actual in-game Rivet Reach multiblock tank. The dark reinforced blocks make the frame, the large panels/glass fill the faces, and the controller/ports replace ordinary side panels.

A 3×3×3 tank is the smallest possible multiblock tank. It has one empty block of interior space and stores 250 L.

In-game block	Count	What it does
Reinforced Tank Frame	20	Every corner and every edge block
Tank Wall	2	Centre of the floor and roof
Tank Controller	1	Required. Forms and manages the tank
Tank Access Hatch	1	Optional but convenient for buckets
Tank Fluid Port	2	One INPUT and one OUTPUT in this example

The Access Hatch is optional because the controller can also accept buckets. Any unused side-panel position can instead be a Tank Wall or Reinforced Tank Glass. A tank must have exactly one Tank Controller.

The diagrams below are top views. Imagine looking straight down at each horizontal layer while building upward.

Legend

• F = Reinforced Tank Frame
• W = Tank Wall
• C = Tank Controller
• H = Tank Access Hatch
• I = Tank Fluid Port whose pipe end is configured as blue INPUT
• O = Tank Fluid Port whose pipe end is configured as red OUTPUT
• . = empty air — do not place a block here

Place 8 frames around the outside and a Tank Wall in the middle.

F F F
F W F
F F F

The result is a completely filled 3×3 floor.

This is the important layer. The centre stays completely empty.

F O F
I . H
F C F

The four corners are frames. The four middle positions on the outside faces are where side panels or functional tank blocks go.

The controller, hatch and ports must face OUTWARD. Stand outside the tank when placing them. Their visible face/nozzle should point toward you, with the empty tank interior behind the block. If one faces inward, open its interface and rotate it in 90° steps.

Close the tank with the same pattern as the floor:

F F F
F W F
F F F

Open the Tank Controller. A correct build should report:

FORMED · 3 × 3 × 3
Capacity: 250 L

Validation also runs automatically when nearby blocks change. RE-SCAN asks the controller to check the structure again.

If it does not form, jump to Troubleshooting.

All tank-component recipes below use the 4×4 Machinist's Bench. They are shapeless recipes: the ingredient positions in the 4×4 grid do not matter. The icons shown here are the same rendered item icons used by the game.

Iron Plate ×3

+

Rivets ×4

+

Copper Plate ×1

→

Frame ×4

For the example tank you need 20 frames, so craft this recipe 5 times.

Machine Casing ×1

+

Iron Plate ×4

→

Tank Wall ×4

Keep some Tank Walls available: the controller, ports and hatch below are themselves crafted from Tank Walls.

Tank Wall ×1

+

Cog ×1

+

Azure Crystal ×1

→

Controller ×1

Every tank needs exactly one controller.

Tank Wall ×1

+

Fluid Pipe ×1

→

Fluid Port ×1

The example uses two ports so it can have a clearly separate INPUT and OUTPUT, but larger designs can use more.

Tank Wall ×1

+

Copper Plate ×2

→

Access Hatch ×1

The hatch gives you another convenient place for 10 L bucket transfers. It is not required to form the tank.

Glass ×4

+

Rivets ×4

→

Tank Glass ×4

Glass can replace ordinary wall panels on the vertical sides. Do not use it in the centre of the floor or roof; those positions require solid Tank Wall.

Bring a Water Bucket and open either the Tank Controller or Tank Access Hatch. Use ADD 10 L to put water into the tank and TAKE 10 L to remove it.

1. Enable a Tank Fluid Port and connect a Fluid Pipe on an accessible face.
2. Hold a Wrench and right-click the tank-facing pipe end until its blue Input arrow points into the tank.
3. Connect the source end to stored water, with a red Output arrow pointing out of that source.
4. For delivery, attach another pipe and set its tank-facing end to red Output with the wrench.
5. Connect its outward-facing nozzle to the machine/tank that should receive water.

Power Cable does not carry water. Fluid, electrical power and Blue Signal are separate networks.

Once the 3×3×3 example works, you can scale the same construction up.

• Each outer dimension may be from 3 to 9 blocks.
• The dimensions do not have to match. For example, 6×4×5 is valid.
• Every corner and every edge block must be Reinforced Tank Frame.
• The centre areas of the floor and roof must be solid Tank Wall.
• The vertical face centres may use Tank Wall, Reinforced Tank Glass or functional tank components.
• The entire inside volume must remain empty air.
• There must be exactly one Tank Controller.
• Controller, ports, hatch, valve and level sensor must face outward.

Capacity is based on the empty interior volume:

(width − 2) × (height − 2) × (depth − 2) × 250 L

Examples:

These are not needed for your first tank.

Craft 1 Tank Fluid Port + 1 Signal Conduit → 1 Signal Valve Port at the Machinist's Bench.

It replaces an ordinary side port. Enable its port, set the adjoining pipe end with a held Wrench, and connect Blue Signal to the keyed signal fitting. ON opens the valve; OFF or no attached signal keeps it closed. Fluid and signal can share a fitted Fluid Pipe while remaining independent channels.

Craft 1 Tank Wall + 1 Signal Wire + 1 Glass → 1 Tank Level Sensor at the Machinist's Bench.

It outputs Blue Signal when the stored percentage reaches its configured threshold. See Blue Signal.

The controller reports the first failed coordinate and highlights that location in the world.

Breaking any shell block suspends normal transfers, but the stored liquid remains with the controller. Repair the shell and let it validate again.

Mining preserves stored liquid. A recovered Water Tank keeps its contents. A recovered Tank Controller carries the entire multiblock tank’s liquid and retained capacity, even after a breach. Shell blocks carry no liquid. Replace the controller and rebuild a valid shell to resume normal transfers.

Filled tanks/controllers each occupy one inventory slot. Their exact contents survive chests, item pipes, drops and saved games. Empty ones stack normally. Select a filled tank in your hotbar and hold Shift, then left-click to discard its liquid while keeping the tank. You can also Shift-left-click an inventory slot with the tank on your inventory cursor. This does not spill a source into the world.

Buckets, normal output ports and RECOVERY OUT remain available to transfer liquid instead of discarding it. Recovery works even when the structure is invalid and lets a Fluid Pipe drain quantities smaller than one bucket.

Actual game captures, 2026-09-13. The recovered small tank retains 12.345 L of lava; the pipe setup transfers lava between two small tanks.

If you resize a tank smaller than its current contents can fit, drain enough liquid before the smaller structure can become valid.

A bank of batteries is a different kind of multiblock and is solid rather than hollow: see the battery-bank guide.

Fluid Pipes can meet any accessible face of a functional fluid port. Direction changes require a selected Wrench and right-click on the machine-facing pipe end. Empty hands, other items and Interact cannot change them. Rotating the tank part does not reverse configured ends. The port interface enables/disables transfer; the wrench chooses each end’s direction. See Pipes.

Seeing your factory from a distance shows current model visibility and an elevated tank view.