Smash the Summer Heat With These DIY Water Weapons!




About: Random Weekend Projects

Bring out the big guns!  Have you ever seen a water balloon shotgun?  Here's how to make a High Powered Water Balloon Shooter that will fire 17 balloons at once!

Step 1: Watch the Video!

WARNING: Adult supervision and adequate training is recommended.  Misuse, or careless use, of equipment or projects may result in serious injury, property damage, and/or death.  Use of content is at your own risk

Step 2: Rocket Rifle & Candy Cannon

This project is a done with a simple modification to some of my previous projects.

My favorite for launching water balloons is the a modification of the "Rocket Rifle".

You can see how to build that step-by-step in this video:

This will also work with the "Candy Cannon" and no modification is necessary.  It's ready "as is" and you can see how to build that in this video:

Step 3: Modify the Rocket Rifle With the Cannon Adaptor

To modify the Rocket Rifle into a Water Balloon Shotgun, all you'll need to do is unscrew the barrel, and replace it with the Cannon Adaptor.

The Cannon Adaptor is simply a 2' length of 2" PVC pipe, a 2" coupling, and some reducer bushings to bring the threads down to 1".  Lastly, a 1", Close (short), PVC riser so it will screw into the sprinkler valve on the rifle.

I added some camouflage paint to match the gun.

Step 4: Shooting Water Balloons

When shooting water balloons, one challenge you need to be aware of, is how the pressure from the gun bursts the ballon before it even gets out of the barrel.

There are 4 steps you can take to get a successful launch.

1. Wadding

You need something that will cushion the pressure on the the balloon as it's launched.  I made some wads with plastic cups.  They are firm, but cushion the balloon enough during the acceleration to keep it intact.  You could also use cloth, or even as something as simple as a moistened rolled up sock.  

You can use the barrel from your rocket rifle as a ram-rod to push the wad to the bottom of the barrel.  It should be as close to an air-tight fit as you can get.

2. Lubrication

If the barrel is dry, the balloon will pop when it's fired.  This is because of the friction during payload acceleration.

I found that using a bit of vegetable oil to coat the sides of the barrel eliminated this problem.  It also helps lubricate the diaphragm in the sprinkler valve to prevent it from locking up.  

Water works as lubrication as well, but over time, the minerals from the water will dry inside the valve and may make it lock up at higher pressures, to the point where the 9V battery isn't strong enough to open it.

3. Size of balloon

The smaller the balloon, the stronger it will be.  I had great results with balloons that had a slightly smaller diameter than the barrel.  If they are wider than the barrel, you can still make them fit, but there will be more friction as they exit, and a greater chance of failure.  

4. Using the right pressure

I found that 65-70 PSI works great for a single water balloon.  At this pressure, you can expect a balloon to fly around 300 feet!

You can fit multiple balloons in the barrel, and will need to adjust the pressure up slightly with each one you add.  

I tested all the way up to 17 balloons at 90 PSI with great results!

Step 5: 17 Water Balloons at Once!

A 2' barrel will hold around 17 water balloons.  This increases of the weight of the payload significantly, so a pressure of around 90+ PSI is recommended for longer distance shots.   Otherwise, they will just plop out of the end.  Funny, but not very effective.

There is quite a bit of kick as the balloons are fired out, so using the Candy Cannon as a Water Balloon Mortar is the easiest option, and the barrel can be tilted for trajectory.

However, using the Rocket Rifle to shoot multiple balloons, has a great and powerful feeling to it that you can't get with the Candy Cannon.

For portability, the manual ball valve near the fill port can be closed, maintaining the pressure charge in your water weapon.  It will probably only be good for 1 shot, but will give you the option to disconnect from the air hose and go anywhere.  

The pressure charge should hold indefinitely.

Step 6:

Well, there's one way to get out and take advantage of the good weather this summer, and keep cool at the same time.

If you haven't seen the video yet, you can still see it here:

And if you missed seeing how to make the Rocket Rifle and Candy Cannon, you can still check them by clicking on the links.  

If you like this project perhaps you'll like some of my others. Check them out at
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    16 Discussions


    5 years ago

    I made one of these for my 2 boys. I bought a bum sprinkler valve so I had to go w a manual ball valve instead but they, and the neighbors love it's! anybody have a super fast way to make water balloons in mass? I'd add I picture but the app doesn't make it clear how to ( if possible!). thanks for helping me make many smiles!

    3 replies

    5 years ago on Introduction

    One of these in the form of the DOA-12 shotgun would be absolutely amazing


    5 years ago

    Would love to make this (these) to entertain the grand kids. I only wish videos would actually play on this App! Not one video -- of ANY project -- will even show up, let alone play. Bummer!

    My son built a potato cannon that works great for this type of thing too except we don't put the water in balloons we just fill the barrel with water and out it comes with a shot of air.
    Thank you for a great tute and idea.


    5 years ago on Introduction

    Excellent. I love your projects, and you make very good videos too.


    5 years ago on Step 4

    A friend of mine built a "spud gun" with a sprinkler valve. He uses two 9V batteries in series to get good valve performance.


    5 years ago on Introduction

    wish this instructable had more of the cannon build and less video of the build


    5 years ago on Introduction

    Made one of these (this design) for the 4th, it was a bit hit. I experimented with different types of wadding and found that a wadded up grocery bag worked really well. I ran a string through the chamber end of the barrel and let it hang out of the muzzle end about 24" where I tied off the grocery bag so I wouldn't have to chase it down after each shot. I had a 2" barrel and was getting 350-400 feet at 65 psi with a single balloon. The only lubricant I used was water, had a breakage rate of one out of fifteen or so, very acceptable.


    5 years ago

    Your videos don't work on the instuctables app please fix