Which Tank Fills Up First?

Water tank puzzles are always more challenging than they first appear. With dozens of pipes, multiple tanks, and hidden blockages, it’s easy to assume the water will travel to the closest container. However, the secret to solving this puzzle is to ignore the clutter and carefully follow the only open route.

Let’s break it down step by step.

Step 1: Follow the Water

The water begins flowing from the faucet into Tank 1.

At first glance, it looks like the water has several possible directions to travel. But before deciding where it goes, you need to inspect every pipe connection carefully. A single blocked entrance can completely change the outcome.

Step 2: Check Every Connection

From Tank 1, the water cannot travel to the right because that route is blocked near the outlet leading toward Tank 2.

Instead, the only open exit allows the water to move into Tank 3.

Once inside Tank 3, the water continues through the left-side pipe network.

Step 3: Eliminate the False Paths

This is where most people get fooled.

Several tanks appear to be connected, but the pipe openings are actually blocked.

• Tank 2 never receives water because its inlet is closed.
• Tank 4 depends on Tank 2’s route, so it also remains empty.
• Tanks 6 and 7 are disconnected by blocked pipe entrances.
• Tanks 9, 10, 11, 12, and 13 may look reachable, but hidden blockages prevent the water from entering them before another tank fills.

The puzzle is designed to distract you with a complicated maze, but only one continuous path remains open.

Step 4: The First Tank to Fill

After leaving Tank 3, the water flows through the open vertical pipe on the left and enters Tank 5.

From there, it immediately continues through another open pipe that leads directly into Tank 8.

Since Tank 8 receives water before any of the lower tanks can be supplied, it is the first tank that fills completely.

✅ Correct Answer: Tank 8

Many players choose Tanks 10 or 12 because they focus on the long pipe running across the bottom of the puzzle. Others think Tank 5 fills first because it receives water before Tank 8.

The important detail is that Tank 5 has an open outlet, so the water doesn’t stay there long enough to fill it first. Instead, it continues flowing into Tank 8, where the water accumulates first.

The best strategy for puzzles like this is simple: don’t follow the longest pipe—follow the open pipe. Check every connection one at a time, eliminate blocked routes, and the correct answer becomes much easier to spot.

Did you guess Tank 8, or did one of the blocked pipes trick you? Let us know your answer before checking the solution! 🚰😄