Home Store Project Ideas Project Guide Ask An Expert Blog Careers Teachers Parents Students

What is the Maximum Intermediate Height for a Siphon?

Difficulty
Time Required Average (6-10 days)
Prerequisites Wood shop experience is helpful for this project.
Material Availability Readily available
Cost Average ($50 - $100)
Safety Adult supervision required

Abstract

A siphon is a handy device for emptying out a liquid reservoir that has no drain. For example, they're great for cleaning fish tanks. An interesting aspect of a siphon in action is that the liquid flows "uphill" for a portion of its journey through the tube. This project asks the question, is there a maximum height for that uphill part of the siphon?

Objective

The goal of this project is to measure the maximum intermediate height that siphon can achieve and remain functioning.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

This idea for this project is from an entry to the 2007 San Mateo County Science Fair, "Siphoning: What Is the Maximum Height Achievable?" (project authors not identified).

Cite This Page

MLA Style

Science Buddies Staff. "What is the Maximum Intermediate Height for a Siphon?" Science Buddies. Science Buddies, 4 Oct. 2014. Web. 21 Dec. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Phys_p052.shtml>

APA Style

Science Buddies Staff. (2014, October 4). What is the Maximum Intermediate Height for a Siphon?. Retrieved December 21, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Phys_p052.shtml

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Last edit date: 2014-10-04

Introduction

If you've ever had to clean out a fish tank, you know the practical value of a siphon. A siphon allows you to drain water from a higher reservoir to a lower one, using a tube that goes up and over the edge of the higher reservoir, then down to the lower one (see Figure 1, below). You can initiate the siphon by applying negative pressure to the lower end of the tube (in other words, sucking on it like a straw). Once the siphon has started, the water will keep flowing on its own.

illustration of the siphon principle

Figure 1. Illustration of the siphon principle. A closed tube allows water to be drained to a lower reservoir from a higher reservoir. Within the tube, the water level exceeds the height of the higher reservoir. A siphon is usually initiated by applying negative pressure to the lower end of the tube. Once the water is flowing, the pressure difference between the inlet and outlet drives the water through the uphill section of the siphon

For part of the trip, the water flows "uphill" through the tube. How can this be? When you suck on the tube, you create a partial vacuum (lower pressure) inside the tube. Normal air pressure, pushing down on the surface of the liquid in the reservoir, then forces some liquid up into the tube. As soon as the water inside the tube reaches the crest and starts flowing "downhill" to the lower reservoir, the flow keeps going on its own. Now the flowing water itself is creating the lower pressure at the drain end of the tube.

An interesting question to ask is: "How high can the crest of the siphon tube be before the siphon fails and the water stops flowing?" This project is designed to answer that question.

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts:

  • Siphon
  • Atmospheric pressure
  • Gravity
  • Partial vacuum

Questions

  • How does a siphon allow water to flow "uphill"?

Bibliography

News Feed on This Topic

 
, ,
Reading level:
Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed

Materials and Equipment

To do this experiment you will need the following materials and equipment:

  • 2 large buckets: 5 gallon (19 L) size works well
  • Sturdy table (for raising height of one bucket)
  • 22 m of clear tubing
  • Water
  • Food coloring
  • Two pulleys (one large, one small)
  • Attachment hardware (e.g., a wood screw) for the small pulley
  • 22 m of heavy string or twine
  • ~10 m tall support for pulleys
    • One idea is to attach a pulley support to a second-floor balcony.
    • Another idea is to construct a 10 m long pole from several pieces of 2" x 4" lumber. The pieces can either be glued or screwed together with lap joints (overlapping sections). The pole will need to be attached firmly to some external support.
  • 10 m (or greater) tape measure

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Experimental Procedure

  1. Do your background research so that you are familiar with the terms, concepts, and questions, above.
  2. Figure 2 below shows the essentials of the experimental apparatus for this project.
    illustration of the siphon principal

    Figure 2. Diagram of the experimental apparatus.

    1. The source bucket (bucket 1) must be higher the outlet bucket (bucket 2).
    2. The source bucket should always contain the same amount of water at the start of each test. Draw a "fill-to" line inside the bucket to make it easy to start with the same water level.
    3. Attach the string securely to the large pulley, then pass the string over the small pulley as shown. The string can now be used to raise or lower the large pulley.
    4. Pass the tubing over the large pulley so that the tubing can be raised or lowered as desired.
    5. Attach the inlet end of the tubing firmly to the side of the source bucket, so that the opening is near the bottom of the bucket.
    6. Tip: if you add food coloring to the water it will make it easier to see whether or not it is flowing through the tube.
    7. Tip: always start with the same amount of water in the source bucket.
  3. Apply negative pressure to the outlet end of the tubing to get the siphon started.
  4. Measure the time it takes to siphon a standard amount of water (e.g., two liters) from the source bucket to the outlet bucket.
  5. Use the string to raise the tubing to successively higher intermediate heights. Repeat the flow rate measurement at each height. Make at least three measurements (more is better) at each height.
  6. Calculate the average flow rate for each height.
  7. More advanced students should also calculate the standard deviation.
  8. At what height did the siphon stop working?

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Variations

  • What happens if you use a different starting height for the source bucket?
  • What happens if you change the water level in the source bucket?

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Ask an Expert

Related Links

If you like this project, you might enjoy exploring these related careers:

Mechanical engineer building prototype

Mechanical Engineer

Mechanical engineers are part of your everyday life, designing the spoon you used to eat your breakfast, your breakfast's packaging, the flip-top cap on your toothpaste tube, the zipper on your jacket, the car, bike, or bus you took to school, the chair you sat in, the door handle you grasped and the hinges it opened on, and the ballpoint pen you used to take your test. Virtually every object that you see around you has passed through the hands of a mechanical engineer. Consequently, their skills are in demand to design millions of different products in almost every type of industry. Read more
Chevron civil engineers examine blueprints

Civil Engineers

If you turned on a faucet, used a bathroom, or visited a public space (like a road, a building, or a bridge) today, then you've used or visited a project that civil engineers helped to design and build. Civil engineers work to improve travel and commerce, provide people with safe drinking water and sanitation, and protect communities from earthquakes and floods. This important and ancient work is combined with a desire to make structures that are as beautiful and environmentally sound, as they are functional and cost-effective. Read more
female mechanical engineering technician

Mechanical Engineering Technician

You use mechanical devices every day—to zip and snap your clothing, open doors, refrigerate and cook your food, get clean water, heat your home, play music, surf the Internet, travel around, and even to brush your teeth. Virtually every object that you see around has been mechanically engineered or designed at some point, requiring the skills of mechanical engineering technicians to create drawings of the product, or to build and test models of the product to find the best design. Read more
Scientist Image

Civil Engineering Technician

Do you dream of building big? Civil engineering technicians help build some of the largest structures in the world—from buildings, bridges, and dams to highways, airfields, and wastewater treatment facilities. Many of these construction projects are "public works," meaning they strengthen and benefit a community, state, or the nation. Read more

News Feed on This Topic

 
, ,
Reading level:
Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed

Looking for more science fun?

Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.

Find an Activity