Introduction: Water Hand Cannon

About: Full time Mechanical Engineer

A few years ago I wanted to buy a bunch of water guns for a summer picknick that was coming up. I looked in the local retail store and there were no Super Soakers to be found. So I became determined that I could build my own water gun. After realizing the complexity of a Super Soaker and the cost to build one out of PVC I simplified my design into what it is now, The Water Hand Cannon.

*I must give credit to some of my inspiration. First was an Instructable on building a Water Mortar.
*My next inspiration was the commercially available Stream Machine that i found at an outdoor sporting store.

The following Instructable will outline the steps to make your very own Water Hand Cannon that will out soak all those Super Soakers.

Step 1: Materials

Materials Needed:
  • 1/2" Schedule 40 PVC
  • 3/4" Schedule 40 PVC
  • 1" Schedule 40 PVC
  • 1/2" PVC End Cap
  • Two 1" PVC End Cap
  • 45o 1/2" PVC Elbow
  • PVC Primer and Cement - Clear
  • Two #15 O-Rings - 1"OD X 3/4" ID -> These can be found in the faucet repair sections of your hardware store

  • Engine Lathe and Tooling
  • Hacksaw
  • 1/4" Drill
  • 7/8" Drill or Foster Bit
  • Deburring Tool
  • Petroleum Jelly
  • Small Scrap Piece of 1/2" and 1" PVC pipe for checking fitting -> 3 to 4" is fine

A bit about size:
Each gun I constructed is about 2' long when collapsed. Smaller guns can successfully be made. I have two 1' Water Hand Cannons that work very well for smaller children and still have the same range as a full size gun. Any smaller then a foot would have a limited water reservoir and be hard to thoroughly soak your victims.
On the opposite side I did make a 3' gun with the hope that the extra foot of water would be an advantage. I found instead that the gun was hard to hold when it is so long (6' filled) and was prone to bending due to the soft  PVC. Anything around 1 to 2' is the perfect length.

A lot about tools:
Unfortunately for some I make extensive use of the engine lathe in building the Water Hand Cannon. I imagine the parts could be turned down using other methods that I have seen on Instructables but using an engine lathe greatly reduces time and will make it easier when making multiple Water Hand Cannons. (Yes you will want more then one for a proper water fight.)
For turning down the PVC I used a round nosed HSS bit. The radius on this bit is about an 1/8th of an inch. By using a round nose bit the finished part will have a much smother finish. This radius also closely matches the needed radius to make the o-ring groove. To make this bit i took an 1/4 inch piece of HSS and added the radius on the end. After having the proper radius I then tilted the grinding wheel table to add the front clearance angle. For cutting PVC a back rake angle is not needed but if you are planing of using the tool for rouging out metals you will want to add this angle while you are making it.
Another operation in this Insturctable calls for a boring bar. You will want one that will be able to clear a 1/2" or smaller hole. The style of baring bar is up to you as long as it gets the job done.
Construction of the nozzle and retaining cap call for a tale stock and drill chuck along with the appropriate drill bits.

Step 2: The Plunger

I like to start with the plunger because it is the key to the Water Hand Cannon. If you can make this part the remaining parts will be easy.

Plunger Cap:

Start by taking the 1/2" PVC end cap and press fitting it on the 1/2" PVC scrap. Make sure the cap is properly seated and the pipe is pressed as far in as possible. The tapered cap should provide enough friction on the pipe that it will not slip when being turned down in the lathe. Now using the 1" PVC scrap as a guide remove material until the cap fits loosely inside. Make sure to remove enough material so that the cap will not bind. I have about a 1/6th to 1/8th inch gap. Now take a file and remove any burs leftover from the turning process. This is also a good time to remove any writing that may have been cast into the face of the cap.

1/2" Connector:

Cut a section of 3/4" PVC about 4 inches long. Now using the 1" PVC guide remove material until the 3/4" pipe fits into the 1" pipe. Cut the turned down section of 3/4" pipe into one inch sections. Then using a boring bar open the inside diameter so the 1/2" PVC scrap will fit snugly inside. You only need one of the one inch sections, I called for a 4 inch section because it was easier to hold in my lathe.

You can also buy 1/2" PVC connectors but these will have to be turned down just like the cap was.

O-Ring Body:

Cut a 2" section of 1/2" pipe. Using the round nosed bit place two groves in the center of the 2" section. Place the grooves about an 1/4" apart. When cutting the grooves always remove a few thousandths of material and then stop the machine and place an o-ring in the grove. Check the fit with the 1" PVC guide. You want the o-rings to have a tight fit into the 1" PVC. The tighter the fit the less leaking but too tight an the rings will bind.

The difficult pieces of the Water Hand Cannon have now been constructed.

Step 3: Nozzle and Retaining Cap


The nozzle is constructed from one of the 1" PVC end caps. Using the tale stock and drill chuck place a 1/4" hole in the cap. With the piece still in the chuck remove any casting marks from the face of the nozzle with a file.

Retaining Cap:

The retaining clip is constructed from the other 1" PVC end cap. Again using the tale stock and drill chuck add a 7/8" hole in the face of the cap. If you do not have a drill bit of the required size use a foster bit or spade bit. The PVC is soft enough that a foster bit or spade bit will cut though like a knife in butter.

Step 4: Body and Handle


Cut a 2' section of 1" PVC pipe for the main body. Cut a 2' section of the 1/2" PVC pipe for the secondary body.


Cut a 4" section of the 1/2" PVC pipe for the handle. Using the lathe square of the ends so that it will look nice for the finished gun.

Now all the pieces for the Water Hand Cannon have been constructed. Using the deburring tool remove lips from any of the cut ends of pipes. Also be sure to deburr the nozzle, retaining cap and the 1/2" connector.

Step 5: Assembly

Assembly begins with gluing the plunger together. To begin place the two o-rings in the grooves on the o-ring body. After adding the plunger cap and connector trying to get o-rings on the plunger will be hard and could damage the o-ring.
Glue the plunger cap in place on one end of the o-ring body. Try not to get any PVC cement or primer on the o-rings. After gluing the cap in place and waiting a few seconds for it to set place the 1/2" connector on the other end of the o-ring body. Glue only a 1/2" of the connector to the o-ring body, you will need to remaining 1/2" to connect the plunger to the secondary body.

Glue the assembled plunger to the secondary body. THIS IS IMPORTANT! Slip the retaining cap onto the secondary body. After gluing the 45o elbow and handle on you will not be able to add the retaining cap. Make sure the retaining cap faces the correct way as show in the picture, open end towards the plunger assembly.

Glue the 45o elbow on the secondary body. Glue the handle into the 45o elbow making sure that the square end of the handle is visible.

Glue the nozzle onto one end of the primary body. Now using some petroleum jelly (Vaseline) insert the plunger/secondary body/handle assembly into the primary body.

The first guns I made 2 years ago I intentionally didn't glue the retaining cap into place. The purpose of this decision was so that I could replace the plunger assembly when the o-rings went bad. I have found that the o-rings do not wear out as fast as I had initially thought. I also found that in the heat of battle the guns would have a tendency of coming apart leaving the wielder to the mercy of their attackers as they fumbled to reassemble the gun. This current batch of guns I have decided to glue the retaining cap into place.

Now you should be done. Now wait a few minutes for the glue to dry before testing on any available targets.

Step 6: Extra

As you may have noticed I painted the guns I made. The first batch of guns I left unpainted but used fine sandpaper to remove any lettering from the manufacture. This time I wanted them to look less like PVC and more like a Water Hand Cannon. I used Krylon spray paint that is designed for plastics. Unfortunately the paint didn't hold up to extended use so now the guns look spotted and scratched.

Another thing I noticed is that the guns have a tendency to sink slowly. This is not a problem if you are using them in a pool or refilling them with a bucket but at the pond that mine where used at if you were not careful they would sink out of site. To prevent this I would consider closing off the handle end to hopefully trap enough air to create some buoyancy. Otherwise spraying some foam insulation into the handle might also work. This is something I will have to try for the next batch.