Introduction: Water Rocket Launcher for Science Fun V2

About: Elementary school teacher and writer with a degree in IT Security and Elementary Education. I have been voiding warranties since 1975. Created a surround sound system at the age of 7. Constructed my own FM tra…

Last year (2013/14), I taught 2nd grade science at IDEA Allan Academy in Austin Texas. When I was handed the assignment, I wanted to do more than lecture and provide worksheets for the subject. Science, like most subjects had to be taught with hands on examples where students would gain more from personal experiences rather than filling out multiple choice answer sheets. As a year-end project, I offered the grade an opportunity to construct water rockets (was a very big hit school wide) and for a selected few, a chance to hold the title of Flight Engineer.

Water Rocket Launcher

As a teacher, I strongly believe that science has to contain an element of fun to keep kids engaged and inspire them to pursue sciences as adults. Many water rocket launchers (WRL) emphasize safety as part of the launching protocols. Typically this means that the kid launching the rocket holds a string to the launcher at a safe (and dry) distance from the launcher. (Blah! - that's no fun).

This launcher is not only very inexpensive (<$5.00) to build, but it places the child to get underneath the launcher allowing him or her to get wet and for virtually every kid in the world, a wet kid is a kid having fun.

Teachers: Flight Engineers are kids supervising the launch. I like selecting middle of the road kids who need something special to look forward to going to school. See the last page for an example launch with on of my Flight Engineers.

Step 1: Materials and Tools

All materials and tools (except for the valve stems) are available at Home Depot or Lowes Home Improvement Stores.


  1. One 10' long 1/2 inch PVC pipe ($1.85).
  2. One 1/2 inch 90 degree elbow ($0.45).
  3. One 1/2 inch pipe cap ($0.45).
  4. One 18 inch long 1 1/2 inch pipe. ($1.25). **Update**
  5. One hose clamp (1 to 2 inch) ($0.90).
  6. A dozen zip ties (can't put a price on these since I buy in mega-bulk).
  7. Duct Tape (I am never without duct tape).
  8. Empty 32oz soda bottle.
  9. Permanent maker.
  10. Large bowl of cold tap-water.
  11. Valve stems - donated by a tire repair shop. Ask by telling the Tire Manager that you're doing a science project and it involves a valve stem. Make sure they are thanked by the students (Thanking Poster).


  1. PVC safety cutter (if kids are cutting the pipe).
  2. PVC saw (if the teacher is cutting the pipe).
  3. 1/4 inch drive socket and ratchet for the hose clamp.
  4. Standard classroom scissors.
  5. Heat gun (preferred) or kettle of boiling water.

Teachers: I have a very strict policy regarding safety and tools around my students. All my Junior Engineers must have eye protection and be seated when handling ANY tool (including scissors). If you kids are going to working with tools - ensure they follow these rules:

  1. Eye protection at all times.
  2. Be seated when handling tools or hazardous materials.
  3. Be mindful of your blood circle.
  4. No horse play.
  5. No excessive talking.

Step 2: Cut PVC

There will be extra PVC after the sections are cut. In most cases, there may be enough to assemble an additional launcher.

1/2 Inch PVC

  1. Cut the PVC into one 2 foot section. This section is the bottom and must be between 18 and 24 inches long.
  2. Cut a 3 foot section. This is the launching section.
  3. Cut a final piece of the PVC into one 6 inch section.

1 inch PVC

  1. Measure the length of the zip ties.
  2. Cut the PVC exactly one-half the length of the zip tie.

Teachers: With the safety cutter, my kids spent 20 minutes cutting one section of the pipe. If there is not time, use a hack-saw. It did not take me more than 5 minutes to cut all sections with the hack-saw.

Step 3: Drill Hole | Install Value Stem

For this, I used donated valve-stems from a local tire shop. If you can, ask for standard tire stems as truck or heavy valve stems are slightly larger.

  1. With a 3/4 inch drill bit, drill a hole in the center of the cap.
  2. Install the valve stem in the end of the cap.

Teachers: This is best done with a drill press. I used a set of channel locks to hold the cap while the drill press did its job.

Step 4: Mark the Spot for the Stopper Bubble

For safety reasons, this step should ONLY be done by an adult or very well supervised middle/high school student.

A bubble in the PVC must be created to ensure a proper seal against the base of the rocket.

  1. Insert the empty 32oz bottle two-thirds of the way into the bottle.
  2. Mark the end of the bottle with a permanent maker.

Step 5: Make the Stopper Bubble

Teachers: This can be a hazardous step and I STRONGLY recommend doing this yourself or asking for a teacher's aide to help.

  1. Using the heat gun, concentrate the on the marked - rolling the pipe round.
  2. While heated , compress the pipe inward forming a bubble. (boiling water can also be used).
  3. After the bubble is formed, dip the bubble in cold water to cure.

Again, hot items and little fingers don't mix well. Using 1-on-1 supervision when kids are handling hot materials.

Step 6: Assemble Launcher Base

PVC pipe cement contains noxious fumes. Recommend completing this step outdoors or in a very well ventilated area.

  1. Insert the 1 inch tube over the bubble tube. Note: The 1 inch tube should be between the bubble and the 90 degree joint.
  2. Insert the pipe clamp under the 1 inch tube - do not tighten.
  3. Apply cement to both sides of elbow joint.
  4. Connect top.
  5. Connect bottom.
  6. Apply cement to 45 degree joint.
  7. Connect 45 degree joint to other end of the bottom.
  8. Attach short piece of the PVC to the other end of the 45 degree joint.
  9. Apply cement to the cap with stem (careful not to get any on the opening in the stem.
  10. Attach stem cap to short pipe.

Once all the pieces are together, visually align the launcher while the cement is still wet.

Allow to cement to dry and set over night.

Step 7: Assemble Launcher Mechinism

This step may take some trial and error.

  1. Cut two inches of duct tape - set aside.
  2. Place the 32oz bottle down until it touches the bubble. The fit should be snug but not tight.
  3. Slide the PVC up to the edge of the bubble.
  4. With the zip-ties place four to six ties between the 1/2 pipe and the inside of the 1 inch pipe with the tie top side towards the bottle (see picture).
  5. Wrap the ends of the zip-ties with the two inch tape.
  6. Continue placing ties until the entire ares around the bottle is covered.
  7. Apply another strip of duct tape.
  8. Secure the ties with the pipe clamp - tighten with a ratchet.
  9. Cover pipe clamp with tape.

The launcher is now ready to test. This is another great teachable moment to talk about safety and safe practices for launching.

  1. Person launching the rocket will kneel down.
  2. Person using the bicycle pump (never use an electric car pump).
  3. Never point the rocket towards another person, car or building.
  4. Person launching the rocket must get wet.

I've made 10 of these for the launch in May (2015). After which I shall raffle these (with a rocket) off to students with the best science notebooks.

Perfect way to enjoy summer through science.

Step 8: Ready for Launch


The moment of fun has arrived.

Teachers: Here is my recommended steps for launching:

You will need:

  • Ample supply of water ( > 5 gallons per 20 student class)
  • Typical bicycle tire hand pump. Don't use foot pumps or electric car-powered pumps. Make the kids work for it!
  • Water rockets -See Instructable.

To launch:

  1. Assign one student to monitor the water.
  2. Fill 1/2 of the rocket with water.
  3. Tilt the launcher to the side.
  4. Insert the rocket onto the launcher.
  5. Push the rocket down until it connects with the bubble. The zip ties should grip the neck of the bottle.
  6. Have the student push the launcher rod up - hard and hold it.
  7. Pump the bottle to about 20 p.s.i.
  8. Start the count down.
  9. Launch.

Students get wet and fun commences.

Take plenty of pictures!