Why is the water Pressure dropping?

water pressure in a water tower

This fun water activity shows how water pressure is affected by the amount of water in a water tower.  See how the water pressure drops as the water tower is emptied of water.

Materials

  • Adult helper
  • 2-liter plastic pop bottle
  • 16 penny box nail
  • Hot pad
  • Large tin can (29oz size)
  • Water
  • Plastic container
  • Tape

Directions

  1. Have an adult help you make three holes in the side of the 2-liter pop bottle.
  2. Take a hot pad to hold the nail while heating the tip of the nail. (We used a candle to heat the nail's tip then pressed it into the bottle while it was resting on its side.)
  3. The two holes should be abou 7 cm apart. Make the lower hole about 5 cm from the bottom of the bottle.
  4. Cover the holes with tape so the water will not leak out.
  5. Fill the bottle with water and recap the bottle while setting up the experiment.
  6. Place the plastic container in an area that will not be affected if some of the water leaks during the experiment.
  7. Place the tin can next to the container and the pop bottle on top of it.
  8. Make a guess as to which hole will shoot a jet of water the greatest distance?
  9. Remove the lid from the top of the pop bottle. Pull the tape off so the holes are exposed. If you are having trouble making the activity work it might be because you left the cap on the bottle.
  10. Watch how the streams of water change as the water pressure decreases.

My Water Cycle activity book contains fun activities for people of all ages. The book is available as an ebook that contains 46 pages of interesting and fun activities.     Myrna Martin

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Science behind the activity

Water pressure increases as you go down in depth. That is why the water pressure at the greatest distance. As the water pressure decreases the water jets decrease in length until they stop flowing.

Towns with water towers use this same principal to move water from the tower to homes and businesses all around the town. The tanks are built to keep an entire days worth of water in the tank in case of an emergency.

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