Fun with Less Kilowatts— Build Heron’s Fountain

By Vernon Trollinger, December 12, 2017, Family

Welcome to Fun with Less Kilowatts! We believe that science experiments at home can be a creative way to engage kids in learning while having fun. They can be educational AND great activities to keep your kids busy and away from the television. Each month, we’ll feature a new science experiment that can be a great resource for parents and teachers.

Build Heron’s Fountain

Heron of Alexandria, also known as “Hero”, lived over 2,000 years ago (between roughly 10 AD to 70 AD) in the city of Fun with Less Kilowatts— Build Heron’s Fountain | Bounce Energy BlogAlexandria in Egypt. He taught mathematics and engineering in the Museum of Alexandria, which also included the Great Library of Alexandria that was partially burned by Julius Caesar in 47 BC. Heron experimented with all sorts of mechanical devices that used air, steam, and water pressure. He’s known to have invented the very first steam engine, known as the “aeolipile”, a programmable “robot” cart using a falling weight for power and string, and a simple fountain that worked by using self-contained hydrostatic energy.

That’s what we’re going to build —Heron’s Fountain. And like the aeolipile and the robot cart, it’s simple, elegant, and almost magical.

How to Build Your Own Fountain Experiment 


Fun with Less Kilowatts— Build Heron’s Fountain | Bounce Energy Blog

  • Several plastic beverage straws or tubing
  • Three 16 oz plastic soft drink bottles with caps
  • A hot glue gun
  • A pair of sharp scissors
  • Power drill and inch drill bit the same diameter as your straws/tubing
  • Water

Directions to Build Your Own Fountain

  1. Choose one bottle to the be the top bottle (water supply), the second for the bottom bottle (air supply), and the last one will be the fountain catch basin.

2.  Start with the caps— Use hot glue to glue two caps together top-to-top. After the glue has cooled and hardened, drill two 1/4” holes through the caps. Drill another pair of holes through the third cap as well. These holes are for the straws to fit through. TIP—Don’t rush while drilling because pushing down on the drill could buckle the plastic. Also, use a very sharp drill bit.

3.  Build the straw-siphons— There are three siphons that make the fountain work:

  • The longest is the drain straw. It must reach from the bottom of the first bottle all the way to the bottom of the catch basin. For our build here, that’s about 20 inches.
  • The next is the vent straw that allows air to vent from the lower bottle to the top bottle. This is about 12 inches.
  • The last is the fountain straw. This reaches from bottom of the upper bottle to the top edge of the fountain catch basin. Ours is 10 inches.

TIP—To join our plastic soda straws, I used a pen to stretch and deform the end of one straw. This allowed me to slide the next section up into it until it held firm.

4.  Build the fountain catch basin— Hot glue the single cap upside down on to the bottom of the top bottle. Once it is cool, carefully drill two holes into the bottle using the two holes you already drilled in the cap as guides. Next, cut the top section from the bottle you set aside to be the fountain catch basin. This piece will catch water from the fountain straw and drain it away.

5.  Connecting the straws —The drain straw goes from the very bottom of the bottom bottle, through the double-ended cap in the middle, and through the single cap at the top. You want the top of this straw to just stick up about 1/2” from where it goes through the top cap.

The bottom of the vent straw hangs down about 1/2” into the bottom bottle. It then goes through the double-ended cap and stops just at the upper part of the top bottle.

The bottom of the fountain straw should be just a little bit above the double ended cap. The straw rises up through the single top cap into the fountain catch basin. You can trim off to be just a little higher than the rim of the bottle you cut to be the basin.

Use hot glue to seal all joints. If you’re using plastic beverage straws, be careful as the hot glue can deform and melt your straws. Use it sparingly and take your time.

Once the joints are sealed, connect the rest of the bottles to the caps.

6.  Stand the fountain upright. Pour water into the basin. The water will drain into the bottom bottle. When it’s full, plug the basin drain with you finger tip and turn the whole thing upside down. The water will flow through the vent straw into the upper basin. This will prime your fountain.

7.  Stand your fountain up again and pour more water into the basin.

The Result

Water will come bubbling up out of the fountain straw! It will dribble into the basin and drain down to the bottom bottle.

The Science Behind This Fountain

When you pour water into the basin, gravity pulls the water down into the drain. The further it falls, the more energy it can exert (called “potential”). When the water drains into the bottom bottle, it has enough force to push air in that bottle out through the vent straw. When that air moves into the top bottle, it pushes the same volume of water out through the fountain straw where it dribbles into the basin. The whole process repeats until all the water in the top bottle has been drained into the bottom bottle.

But, can the design to be made to move water continuously in what’s called “perpetual motion”? But isn’t that impossible? Good question! Check out this variation on Heron’s Fountain to see for yourself!

Check out more kid-friendly science experiments from Fun with Less Kilowatts!

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