How To Drain The Reservoir In Blue Prince

So, you want to drain the Reservoir in Blue Prince? This area is found in a massive cavern and, if it's your first time discovering it, you just know that something's down below. While you might already have an idea of what to do, things can get a bit complicated once you're back inside the manor. In any case, we want to remind you that this guide contains spoilers.

How to drain the Reservoir in Blue Prince

The Reservoir is a huge area found in the Underground. It's what separates the two halves--i.e. west (Fountain entrance) and east (Foundation entrance).

You can fully drain the Reservoir by using the controls in the Pump Room. The process is akin to what you did for the Fountain. But there's a big difference this time:

• Remember: You have to draft a Pool first just to make the Pump Room appear as a drafting option.
• The Reservoir has 14 water levels. Just like math, you can think of this as +14, and we have to bring it all the way down to zero.
• The Pump Room's main tanks, by default, cannot hold that much water. You need to use the reserve tank, which can only be powered up via the Boiler Room.

Thus begins the most convoluted step if you want to drain the Reservoir in Blue Prince. Basically, you must have a Boiler Room drafted in the house. Once you've activated it, you must ensure that power can be funneled to the Pump Room.

• There must be an unbroken connection/pathway between the Boiler Room's openings and the Pump Room's openings.
• You can form this path via gear-type rooms with doorways (i.e. Security, Workshop, and others), or via red rooms (i.e. Gymnasium, Archives, and others). You'll notice that these rooms have ducts/shafts that lead to a location.
• Make sure the Boiler Room's control panel slider is pointing toward the direction of the shafts/ducts leading to where the Pump Room is located.
• Alternatively, you can make use of the Aquarium as long as it has the Electric Eel upgrade. This also acts like an activated Boiler Room.

Once the Boiler Room is connected to the Pump Room and the reserve tank is powered up, you'll see that the reserve tank's controls can be tweaked. It has options that allow you to drain or fill Tank 1 only.

• Basically, you need to gradually drain water from the Reservoir, and then funnel the water to Tank 1 and Tank 2.
• Use the main tanks to fill up other locations, such as the Fountain, Pool, and so on.
• Once those locations are filled, drain the Reservoir's water into Tank 2 first. Then, drain it into Tank 1.
• If Tank 1 is full, use the reserve tank's controls to take in all the water.

Note: It's fine if you don't have enough steps remaining to make it back to the Underground. As long as you kept this configuration in the Pump Room, the Reservoir should still be drained in succeeding days/runs.

After you fully drain the Reservoir in Blue Prince, it's time to revisit the area in the Underground so head back down via the Foundation elevator.

You'll notice that there are several locked boxes, so make sure you have enough keys. Several of these boxes have clues--i.e. the notes in green are lies or there's a reward in a chest that's not in the water.

For now, try to go all the way to outer edge of the basin. There, at the back of a rock formation, you'll notice a black trunk with a flame symbol. Open it to receive a Sanctum Key. There's also a white box with a sun symbol that's not in the water, and it has an Allowance Token.

Note that, as of the time of this writing, we're unable to confirm if the clues or boxes change. Hopefully, you do get lucky with the crates that you open.

That does it for our guide on how to drain the Reservoir in Blue Prince. This isn't the only thing that you can do in this location, since you can actually sail on the boat. There are also other Sanctum Keys to acquire inside, outside, and underneath the manor.