> For the complete documentation index, see [llms.txt](https://create-deep-seas.gitbook.io/create-deep-seas-wiki/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://create-deep-seas.gitbook.io/create-deep-seas-wiki/deep-seas/diving/ballast-tank.md).

# Submarine Ballast Tank

<img src="https://1371052705-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FV22FKtcNjWW37kUFLLdR%2Fuploads%2Fgit-blob-805162a82d8d0b9cbf417b35f824215e97331a7a%2Fballast_tank.png?alt=media" alt="Submarine Ballast Tank" width="128">

The Ballast Tank is what makes a submarine go up and down. Fill it with sea water and the submarine gets heavier and dives, empty it and it climbs back up.

## Recipe

![Submarine Ballast Tank recipe](https://1371052705-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FV22FKtcNjWW37kUFLLdR%2Fuploads%2Fgit-blob-30d5f7e5591dc7e19dec4f9b6c157f091f6271d7%2Fballast_tank.png?alt=media)

## How to use it

1. Place the tanks inside the hull. Tanks that touch each other form one group and share their water, so you can stack them into a big tank.
2. Pipe the group to a [Ballast Vent](/create-deep-seas-wiki/deep-seas/diving/ballast-vent.md) through a pump.
3. Pull water in from the vent to dive, push it back out to rise.

Each tank holds 8 buckets. The submarine does not care where the water is, it looks at the fill level of all its tanks together: empty climbs, half full holds its depth, full dives. The details are on [Diving and surfacing](/create-deep-seas-wiki/deep-seas/mechanics/diving-and-surfacing.md).

## How many do I need?

One tank drives about 75 blocks of submarine. Count your blocks, divide by 75 and round up: that is all you need, do not add more. Too few tanks and the submarine still moves, just slowly, and a heavy one may never climb back up.

{% hint style="danger" %}
**Use as few Ballast Tanks as possible, and as many Pump Controllers as you can, on a fast shaft (256 RPM).** Every tank is 8 more buckets to pump in and out. Too many tanks with too few or slow pumps, and the submarine takes ages to dive and to climb back up.
{% endhint %}

## Good to know

* Water coming from a Ballast Vent goes in as fast as the pump can push it. From any other source (a fluid tank, another pipe network) it trickles in, so always fill from the vent.
* Only water goes in. Other fluids are refused.
* Look at a tank with Create's Engineer's Goggles to see how full the group is and how many tanks are connected.
* A tank holds down to 400 m before it cracks, deeper than most hull blocks.
* The tanks keep the submarine level too: a submerged submarine slowly rights itself on pitch and roll.

{% hint style="success" %}
**Details to look for**

* Stacked tanks connect like Create's fluid tanks, with top, middle and bottom models.
* Placing a tank on the top or bottom of another one copies the whole layer you clicked on, up to 64 tanks at once. Sneak to place a single tank.
  {% endhint %}

## Video

{% hint style="info" %}
Video coming soon.
{% endhint %}