August 5, 2014

Water rockets are loads of fun! This episode will show you how to build a water rocket launcher out of parts from a hardware store.  It can be made for around $10 in just about an hour.

Episode 10: Build a water rocket launcher

This summer I ran three classes called Rocket Science in the Park for the Passport to Boise Program (Which as been a smashing success in its first year–If you haven’t checked it out you should click here).


rocket science sign


Kids came to my class and learned a little about the physics behind rockets and then built and launched their own water rockets made out of 2 liter water bottles.


demo with the kids


filling the rocket with water



Check out this awesome video that Tobe Brockner filmed for us:

We had some serious fun!

The water rockets are super easy to make (just tape some triangular fins on a water bottle, maybe add a nose cone if you are really ambitious and fire away).

The launcher is a little more tricky however.  I had a lot of people want to know how to build one.  There are tons of plans and videos on the web about building launchers, but I wanted to make a version that was as straightforward and easy as possible.

So, here’s my design…

Supply List:

  • Two 1/2 inch threaded pvc pipes 24 inches long (I used the dark gray pipe-schedule 80)
  • 1 threaded 1/2 inch 90 degree elbow
  • 1 threaded 1/2 inch end cap
  • pipe thread tape
  • pack of cable ties (zip ties)–you’ll need 8, I used the 8 inch ones
  • duck tape
  • adjustable clamp
  • tire valve stem (from walmart or autoparts store)
  • string
  • scrap board(s)

a pic of water rocket launcher

Project video

You may have noticed that his water rocket launcher I showed you how to build is not the same as the ones used at our Rocket Science in the Park Class.  Those launchers both use a scissor system to hold the bottles in place, a rubber stopper with a hole, and hose instead of PVC.  It is a little safer (remember the warning from the video: PVC can shatter under pressure) but costs a little more and it’s tougher to get your hands on rubber stoppers without ordering them online.  If you are interested in that system you can find similar plans here.


  • It seems that about 1/3 the way full of water works the best for the water rockets.
  • You’ll probably want a large open space to launch your water rockets.  I used our backyard some (which is fairly small) and we were constantly having to go into the neighbor’s yards to chase down our rockets:)
  • The launcher make take some tinkering to get to work properly.  Sometimes certain 2 liter bottles seal a little better or worse and you’ll have to adjust your rocket launcher a little.
  • There are better systems than using duck tape on the white pipe to make it a tighter fit on the zip ties to prevent it from releasing too soon.  Sciencetoymaker has a good solution for that here.


Now go build a water rocket launcher and Get Stoked About Science!