How to make an air-powered water balloon cannon



Before starting this project, we’ll need to travel to the local hardware store and acquire the parts.  You can find the parts list for this projects at the bottom of the page.

To get started we’ll need to cut two 12″ pieces of 2″ PVC pipe and six 3″ pieces of 1″ PVC pipe.  I used my compound miter saw to cut the PVC.  When cutting PVC with a power saw, be sure to use a segmented blade.  Using a standard blade could result in dangerous kickbacks.  And of course, regardless of the method you choose, always wear good eye protection.  After we get the PVC pipe cut its time to test fit all of the components.  Let’s start by assembling the pressure tanks.  The pressure tanks are connected by a 1″ PVC tee.  Another tee is added to split incoming air from outgoing air and will be connected to our firing mechanism which is a simple water sprinkler valve.

On top of the tee we’ll add a 3/4″ ball valve.  This will allow us to charge the tanks and close the system for portable firing.  Now, we need to take one of the 1″ caps and drill a 1/4″ hole in it for an air compressor quick release.  This is how we will pressurize the cannon.  It’s attached directly behind the ball valve.  Then just add the 24″ firing barrel and assemble the detonator!

Once we’re happy with the fit, it’s time to glue it all together.  Be sure to use the proper PVC primer on all of the joints before we start gluing, as it will help prevent leaks. Now its time to apply the PVC cement.  I like to push the parts together tightly and then twist them 1/4 of a turn.  Some of the bigger fittings can be very difficult to fit together, and can require a lot of force, so don’t let the glue dry too long before mating them.  Be sure to get the alignment right on the elbows because you won’t be able to adjust them later.

Now, lets strip the wire back about 1/4 of an inch and connect the momentary switch to the 9v battery snaps and doorbell wire.  I prefer to solder the joints and use heat shrink to cover them.

Next we mount the momentary switch through the hole we drilled earlier in the 1 1/4 inch PVC cap and slide the wire through 5″ length of the pipe. I thought the wiring needed some cleanup so covered it with this back tubing for a super clean look!

With everything assembled, its time to attach the air compressor and give it a test fire.  I just placed a paint cap over the end and pressed the detonator.  It worked!

I want my Water Balloon Cannon to look awesome so I decided to paint it yellow and black.  First I painted the yellow and then taped it off carefully.  Be sure to wait 24 hours for the paint to cure completely before applying the masking tape.  Once that’s done were ready to paint the black components and then gently remove the masking tape.

Finally, we’ll apply pipe thread tape to all of the threaded joints before final assembly. And that’s it!  It’s ready to fire!  Before the first firing, we need to lubricate the barrel with some vegetable oil.

And the first shots a success!  But my second shot missed…  I put a back piece of foam down the barrel and fired it at 120 PSI to give you an idea of just how powerful it is.  Easily traveling hundreds of feet into the air.


Parts List
Qty     Item

1          2″ SCH 40 Pipe
1          1″ SCH 40 Pipe
2          2″ Caps
2          2″ Couplers
3          2″ to 1″ threaded reducers
3          1″ threaded to 1″ adapter
1          1″ elbow to threaded 1″ elbow
2          1″ Tee
1          1″ threaded sprinkler valve
1          1″ 90 degree elbo
1          1″ ball valve
1          Air compressor quick adapter.
1          2″ Coupler
2          1″ caps
1          Momentary switch
1          25 ft doorbell wire
1          plastic wire wrap
1          Yellow High Gloss
1          Black High Gloss
1          Pipe Primer
1          Pipe Glue

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