In Blue Prince, few things are what they seem. The elegant Fountain that sits outside the manor may appear ornamental, but it's actually hiding something much deeper. Underneath it lies a staircase to the Underground, and unlocking this hidden area requires solving a cleverly designed water management puzzle involving the Pump Room.

This guide walks you through the entire process of draining the Fountain and uncovering the secrets beneath it.

Reaching the Pump Room

The first step in draining the Fountain is gaining access to the Pump Room. This isn’t guaranteed from the start of every run, as the game’s room drafting system relies on a bit of luck. To unlock the possibility of getting the Pump Room, you first need to draft a Pool. Once that’s added to your layout, the Pump Room, along with the Sauna and Locker Room, becomes available in the draft pool.

From there, it’s a matter of waiting until the Pump Room appears as one of your daily room choices. It may take a few attempts, but eventually, it will show up.

How the Pump Room Works

The Pump Room is a deceptively complex space, filled with tanks, pumps, and a control board. Here's what you'll find:

• Two main tanks (Tank 1 and Tank 2), plus a reserve tank that can be ignored for this objective.
• Three front pumps with levers: Pump 1 (left), Pump 2 (middle), and Pump 3 (right).
• A fourth pump, Pump 4, positioned at the back of the room.
• A switch near Pump 4 that lets you toggle between Tank 1 and Tank 2.
• A control board showing which rooms are connected to which pumps.

Each lever has three positions. Pulling it down fills the selected location with water. Pushing it up drains water from that location back into the tanks. Leaving it in the middle disables the flow. To manipulate the Fountain, you’ll mainly be using Pump 2, which is tied to both the Fountain and the Reservoir.

How to Drain the Fountain

The Fountain starts completely full, represented by twelve blue pips on the control board. Your objective is to reduce that number to zero.

Begin by using Pump 2 to start draining the Fountain. Flip the switch at the back of the room if necessary to alternate between Tank 1 and Tank 2, giving you more space to redistribute the water.

Once you’ve started draining, you’ll need to offload that water elsewhere. Fortunately, several other rooms can accept it:

• The Kitchen can hold three pips of water.
• The Greenhouse can take four.
• The Pool can take one.

That’s eight pips accounted for, leaving four more to be dealt with. These remaining pips can be drained directly back into your tanks using Pump 2, bringing the Fountain’s level to zero.

Once this process is complete, the Fountain will remain drained in future runs unless you manually change the Pump Room’s configuration again.

What Happens After the Fountain is Drained

With the Fountain fully drained, return to the area outside the manor. You’ll now see a staircase leading down into the depths. However, the door at the bottom will still be locked. To proceed, you’ll need the Basement Key, which can be found in the Antechamber.

Once you use the Basement Key to unlock that door, any Underground area you access through it will remain permanently open for future runs. This marks the beginning of a whole new set of challenges and discoveries in Blue Prince.

Draining the Fountain in Blue Prince is a layered puzzle that combines exploration, planning, and a bit of luck. It’s also one of the game’s more satisfying moments, unlocking a previously hidden world that deepens the mystery and expands your understanding of the manor. If you’ve made it this far, you’re well on your way to uncovering everything Blue Prince has to offer beneath the surface.