Need a cool activity to keep the kids busy? How about a LEGO water STEM challenge? Create a dam with LEGO bricks and add water for a hands-on activity that explores engineering, water flow, and problem-solving skills. Of course, you can take this fantastic LEGO building idea outside and set up the hose too!

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Explore the Flow of Water With LEGO

Try this fun LEGO water activity! Can you use your LEGO bricks to control the water flow on an inclined surface? Have you ever been to a children’s museum or science museum with base plates, bricks, and running water available for kids to adjust the water flow or create dams? This is our at-home version of an activity we love at the museums.

Take a Look: Water Experiments for Kids

Building dams is a terrific hands-on STEM activity for kids using a favorite building material, LEGO! A LEGO volcano is another incredible LEGO building challenge with a science theme!

Free LEGO Challenge Calendar

Prepare for a year filled with cool challenges like this LEGO water activity to do with your brick collection! Grab this free printable LEGO challenge calendar guide to get started.

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LEGO Challenge Calendar

Check out the LEGO video below and bonus links at the bottom of the page for more great LEGO-building challenges.

Quick LEGO Water Activity Ideas

  • Build a LEGO boat that floats in the tub, sink, or pool!
  • Sink a brink challenge. Can you make a LEGO brink sink?
  • LEGO wash sensory bin: Add your LEGO to a bin of soapy water and let the kids scrub the bricks and figs
  • Build an underwater ocean scene on a baseplate, place it in a container, and fill it with water (hint: you have to keep it from floating)
  • Build LEGO sea creatures with ocean theme challenges.

How To Build A LEGO Dam

You can try this inside or outside, but be ready to get wet! Set this LEGO water activity up outside near a hose on a hot day.

Supplies: 

  • LEGO Baseplate
  • LEGO 2×2 and 2×4 Bricks
  • LEGO Slopes {assorted sizes}
  • LEGO Hinged Pieces {2}
  • Tray or Shallow Bin (to catch water)
  • Bottle of Water or Hose (to test your design)

How To Build A Dam

NOTE: This is just one building suggestion! Encourage your kids to build their own design.

Check out how we set up our inclined surface below. You may need to adjust your design depending on the variety of available bricks and pieces.

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Once your inclined plane is set up and on a tray or bin to catch the overflow, it’s time to design your dam! This LEGO water challenge and different building abilities are perfect for multiple ages to work on together.

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Younger kids will have fun building and exploring, while older kids can apply the engineering design process to extend their learning.

TIP: You can review the engineering design process steps and print out a free guide here.

You can make your LEGO water dam as complex or simple as you like and repeatedly tweak your design for desired results. You can also encourage older kids to sketch a design first, write predictions, record observations, and analyze the results to conclude the effectiveness of their design.

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I am pretty sure the most fun part of this LEGO water project is pouring the water! This would make an excellent outdoor STEM activity as well.

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Will your LEGO water dam hold up to the testing? Design one today!

More Favorite LEGO Activities

If you love this LEGO water activity, we have plenty of hands-on LEGO activities to keep kids busy. Click on the links below to check out how we love to use our LEGO for STEM challenges.

Enjoy our free LEGO printable sheets for kids, perfect for home and classroom use! Encourage a love of learning by incorporating a kid’s favorite building toy!

Printable LEGO Brick Building Project Pack

Grab the whole Brick Building Fun Pack in our SHOP

All of our printable LEGO challenges as well as exclusive activities. Plus, you will be sent a new link anytime this bundle is updated.

  • 10O+ Brick theme learning activities in an e-book guide using the bricks you have on hand! Activities include literacy, math, science, art, STEM, and more!
  • Brick STEM activity challenges complete with instructions and examples such as a marble run, catapult, balloon car, and more.
  • Brick Building STEM Challenges and Task Cards keep kids busy! Includes animals, pirates, space, and monsters!
  • Landmark Challenge Cards: Virtual tours and facts to get kids building and exploring the world.
  • Habitat Challenge Cards: Take the challenge and build your own creative animals in their habitats
  • Brick theme I-Spy and Bingo games are perfect for game day!
  • Screen-free coding activities with a brick theme. Learn about algorithms and binary code!
  • Explore mini-fig emotions and much more.
  • A complete year of Brick themed seasonal and holiday challenges and task cards
  • Brick Building Early learning pack filled with letters, numbers, and shapes!
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