Introduction: Easy-Peasy PVC Water Gun

Picture of Easy-Peasy PVC Water Gun

There are a handful of do-it-yourself PVC water guns on the internet.

This water gun is similar to other versions out there, including this one I shared a few years ago, but with a handful of new tricks to simplify the design and make it easier for people to duplicate.

If you make a few, let me know how it goes in the comments.

Thanks for taking a look!

Step 1: How It Works

Picture of How It Works

This type of water gun is basically a large syringe. There are two main parts: the outer piece which is the barrel, and the inner piece which is the plunger, or piston.

On one end of the piston there is generally some type of seal, that acts as a round, watertight squeegie. This seal allows the piston to draw water into the barrel as you withdraw the piston from the barrel, and to force water out as you push it in.

The hardest part with this style of homemade water gun is the seal. If it's either too tight or too loose, the gun won't work. There are a lot of complicated ways to make an effective seal, but I believe I found a simpler way to get the same results, quickly and easily. I'll explain as we go.

Step 2: Materials

Picture of Materials

First off, I recommend making six water guns at once. This maximizes the use of materials and should only cost around $30 total. Plus, six water guns seems to be the right number needed to start a decent neighborhood water fight.

Here's what is used to make one water gun:

  • 20" of each: 1" and 1 1/4" PVC pipe (usually available in 10-foot sections, hence the suggestion to make six water guns at once)
  • End cap for each diameter of pipe
  • One 3/4" plug (generally for use on 3/4" pipe)
  • Two o-rings with inside diameter 28mm, outside diameter 34mm, width 3mm. I found these in the hardware bins at an Ace hardware. If you can't find this size, you may be able to use whatever close size of o-ring you can find, using the adjusting method I will cover ahead.

Aside from the o-rings, I bought all my supplies at a Home Depot store.

The only problem I foresee with this water gun design is that the style of the crucial PVC piece--the 3/4" plug--varies depending on the store and who their current supplier of PVC fittings is. That may be a speed bump for some, as well as being able to find the correct o-ring size.

Now, the real secret to this design is dental floss. Yes, the humble, single-use tooth thread that sits undisturbed in your medicine cabinet. You might as well just move it to the workshop where it will see a little more use. It's actually quite handy stuff.

Step 3: Cut Pipe

Picture of Cut Pipe

Begin by cutting 20" sections of pipe. The simplest way to do this is to use a power miter saw. But there are plenty of other ways if needed.

To speed up the process, slip the 1" pipe into the 1 1/4" pipe before cutting.

Step 4: Assemble Barrel

Picture of Assemble Barrel

Drill a 3/16" hole into the center of the 1 1/4" cap, and use PVC cement to glue this to an end of the 1 1/4" pipe. Follow the directions on the cement bottle.

Tip: I sanded off the raised logo on the cap to give me a flat surface to start the drill bit when drilling the hole, and used a drill press to make sure the hole was as straight as possible.

Step 5: Assemble Piston

Picture of Assemble Piston

The 3/4" plug is not normally used with 1" pipe, so it won't fit as is.

To make it fit, I used a sanding drum on my rotary tool to sand down an inch or so of the inside of the 1" pipe, until the plug could be inserted and withdrawn without too much trouble.

Place two o-rings onto the plug and mark their height with a pencil.

Glue the plug into one end of the 1" pipe with cement, just up to the line. You do not want the o-rings to be pinched tightly between the flared end of the plug and the pipe, so a little wiggle room is desirable (1/32" extra or so is fine).

Glue the 1" cap onto the other end of the 1" pipe, which becomes the handle. Other fittings could be use if desired, such as a T or elbow.

Step 6: Adjustable Pressure O-rings

Picture of Adjustable Pressure O-rings

And now for the main trick!

Wrap about 30 feet of dental floss tightly and evenly into the gap between the end of the plug and the end of the pipe on the piston. Leave a loose "tail" of a few inches.

Place the o-rings over the dental floss, and check the fit of your nearly completed seal into the open end of the barrel. It should just barely fit with a little pressure. If it is too tight, simply pull a few inches of the dental floss at a time out from beneath the o-rings, and test until you get the right fit in the barrel. You don't even need to remove the o-rings unless you need to add more floss. When the seal is working properly, trim off the loose floss and you're done.

There is a little bit of trial and error required here, but after the 2nd or 3rd water gun for me I had a pretty good feel for what amount of pressure the seal needed to have to function properly.

I recommend doing this step outside next to a full bucket of water, in conjunction with the next step.

Step 7: A Little Bit of Lubricant

Picture of A Little Bit of Lubricant

Spread a little bit of petroleum jelly onto the o-rings, as well as to the inside edge of the barrel end.

You only need a little; too much will actually be less effective.

Step 8: Have a Water Fight!

Picture of Have a Water Fight!

After a little testing and adjusting the o-ring seals, you should have a pile of awesome homemade water guns for you next big water fight!

Let me know if you make some. Thanks again for looking!


Helijin made it! (author)2014-07-02

Awesome design! I made six of these. I couldn't find an acceptable plug, except for one that was a reducer, so I used a 3/4" (slip) to 1/2" (threaded) reducer and threaded a 1/2" plug into it. It cost a little more, but the reducer gave me the lip I was looking for to retain the o-rings. All of the 3/4" plugs I found didn't have a lip on them or were hexagonal with minimal lip. I also used a 3/4"x1"x3/4" T for the handle. I really like the idea of using floss to adjust for the o-rings - it worked great. I got the o-rings at Lowe's - item number 0544 by BrassCraft or 1-1/8" I.D (1-3/8" O.D) x 1/8" Wall. This was the closest I found to the metric requirements in the instructions. One other thing for clarification, both the 1" and 1-1/4" PVC pipe is Schedule 40 (thick wall.) Thanks for sharing your design.

thedarkener (author)Helijin2015-08-28

I bet the T handles are great, I fear pinching skin in the original design, but caps are already glued on. I just open-palm it.

seamster (author)Helijin2014-07-02

Excellent work! Good job making it work with what you could find. That is the trick with this sort of project.

Thanks a bucket-full for the great tips and photos!

chestersgarage made it! (author)2014-06-15

Made a batch of these this weekend with my kids. Super easy! The 3/4" caps we found fit into the 1" pipe with the force of a hammer. Didn't have to sand/shave at all. I thought I could get away without using floss, but it's required to be able to draw water into the barrel. And we added pistol grips! :) Thanks for the great 'ible!

seamster (author)chestersgarage2014-06-16

Awesome! I like the angled grips.

I noticed a couple of ours stopped sucking in the water as well as when they were first made, so I had to add a foot or so of floss to readjusted the fit of the o-rings. Good as new! (Just a thought, in case yours do likewise after some use.)

Thanks for the photo! Glad you were able to make some.

Moodle2 (author)2016-08-09

did you get this design from a Popular Science magazine? just wondering, 'cuz the design looks similar

seamster (author)Moodle22016-08-09

It looks like Pop Sci was most likely inspired by this:

seamster (author)Moodle22016-08-09

No, but similar piston-type pvc water guns have been around for years.

As far as I know, the o-ring plus dental floss idea is all mine.

Check the publication dates, Pop Sci very well could have gotten some ideas from me! ;)

Shimon - Stan (author)2016-08-02

Great design!

If you make the outer 1 1/4" pipe half an inch or an inch shorter than the inner 1" pipe, you can assure that no one will get pinched.

Donny Halim (author)2016-06-13

great job..

Numbuh1 (author)2015-09-04

is it air-tight??

seamster (author)Numbuh12015-09-04

Hmm. What do you mean?

It is water-tight, till you shoot it out.

Mike4866 (author)2014-06-12

Great job! I've tried to make these before, they're great on raft trips, and always had trouble with the seal. Might I suggest that you make the plunger a couple of inches longer than the barrel to eliminate the pinch factor where the end cap of the plunger meets the barrel.

thedarkener (author)Mike48662015-08-28

I bet a good compromise would be to put a buffer/stopper on the smaller pipe of some sort. Not sure exactly what would fit, should be spongy and durable though..

seamster (author)Mike48662014-06-12

Thanks! Good point on the pinch factor. I actually considered that, but opted to simplify things in order to get the most out of my material using the dimensions stated. This way there is virtually no waste, although we do risk a few pinched fingers.

Perhaps a more pressing issue is that they don't float. I didn't do it, but there's got to be an easy way to modify a pool noodle to slip over the barrel, for folks like yourself that would use these on boats.

pattiemelt (author)seamster2014-06-12

Have you thought of using foam pipe insulation as a float? They're made to slip over pipe & some are even self-sealing so if you can find one exactly the right size, the adhesive can be used to stick to the barrel so it won't slip off. And they're cheap, 6ft for about $2.

pattiemelt (author)pattiemelt2014-06-12

I meant to say "... so if you can't find one exactly the right size..."

seamster (author)pattiemelt2014-06-12

I hadn't thought of that. But it's an excellent idea! Thanks, pattiemelt!

Maybe if someone gives it a try they can post a comment and share their results.

thedarkener (author)2015-08-28

I'm in the middle of making 6 of these according to these awesome instructions. Only difference with mine are the plugs have a hexagon shape instead of round on the outer edge. Still works fine as the rubber O-rings extend past the diameter of it. Had to buy some extra floss, that's the last part. I drilled a 5/16 hole as that was the one plastic drillbit I had in my tool box. I haven't tried with smaller, but the bigger hole tends to "spray" but still accurate (reminds me of the spreader gun in Contra and Super C). We're going to paint these, 3 red and 3 blue (teams) and while it's still hot out have some fun skirmishes with the kids. ;) Thanks for the instructions, this is a really fun project!

lindbergh27 made it! (author)2015-08-13

I just finished a half dozen of these myself last night. My brother couldn't help starting some trouble the first chance he got. He unloaded the contents of one into my back as soon as I turned it. I can't wait to you use them at our family reunion tonight!

seamster (author)lindbergh272015-08-13

Awesome! Thanks for the comment and for the photo. Glad you were able to make some!

lindbergh27 made it! (author)2015-08-13

I made a half dozen myself. Really cool gun! My brother couldn't resist starting up some trouble the first chance you got with one. As soon as I turned my back he unloaded the contents into my shirt.

I can't wait to take them to my family reunion tonight!

tbird2340 (author)2015-07-11

Not having any luck with mine.. I got the 1-1/8" I.D (1-3/8" O.D) x 1/8" O Rings but they get stuck in the tube when I pull it back out.. That's without any floss or tape so not sure that's the reason..

Thoughts? Thanks

seamster (author)tbird23402015-07-11

Hmm. Sounds like the o-rings are either too big, or you need some lube. (Getting slightly smaller rings allows you to stretch them to fit as needed . . . too big of rings and there's no real way to make them work.)

Just a couple thoughts, good luck!

ThisIsSteve (author)2014-06-18

Nice job great instructable.

Posh Josh (author)ThisIsSteve2015-07-05

Thanks mate

MathewO (author)2015-06-16

Just made one. I was able to get everything at a box store. I bought the O-rings at Home Depot. PartsmasterPro #218 O rings.

I used plumber grease, or silicone grease. This is a better alternative to Vaseline.

I used teflon tape instead of dental floss. This works better. For one thing, it's easier and faster to apply. Also, because it's 1/2 wide, you can use it to widen the flange on the 3/4" plug at the same time. I had trouble with dental floss because the O-rings would just slip off when I pulled back on the piston. I started with 20 wraps and then added ten more at a time until I had the correct fit.

ar_caver (author)2015-02-08

I've got to make one (or six) of these! How far do they shoot?

seamster (author)ar_caver2015-02-08

Pretty far! The stream breaks up and turns to mist at about 50 feet, I'd say.

johnstat000 (author)2014-08-25

Looks like a lot of fun! Someone could make this out of cpvc and turn it into a homemade nerf gun!

renokid made it! (author)2014-07-24

I used a 3/4" pipe as the piston with a coupler on the end which allowed a 3/4" plug to go perfectly into the coupler and correct depth too, with this there is no need for any sanding down of the plug. This was my first run, and I plan to improve the shaft of the piston as it's 3/4" and slightly sloppy but works fine. It shot water over 40 feet.

seamster (author)renokid2014-07-24

Very cool, glad you were able to make one!

danpritts (author)2014-07-15

I couldn't find plugs that were the right size - one i bought was too big, and needed to be cut down. The other was too small and the o-ring kept coming off into the body. I ended up using the too-small size, and cutting a slot in the pipe to hold the o-ring.

To cut the slot, i used a hacksaw - the mini "handle" kind worked well. And as always when cutting PVC, doing it on top of the trash can to collect the sawdust helped a lot. A standard perpendicular cut worked well to start the slot, and then to widen it I held the hacksaw at about a 45 degree angle.

I used a 90 degree adapter as the handle, similar to Helijin's T handle. I think this worked better than an end cap would have.

The dental floss worked great, thanks for the tip.

seamster (author)danpritts2014-07-15

Good tips! Thanks for the comment and photos. Glad it worked out for you.

I've noticed on mine that the around the o-rings the vaseline has turned black, I'm assuming from the rubber breaking down a bit. Also I've had to add a foot or so of additional dental floss to each one to maintain a good seal. So they need a little occasional maintenance to keep working right, just like most things I guess!

bogie7129 (author)2014-06-19

My younger brother made some of these, enough for five male siblings. The one thing I remember about they way he built his that is different from yours is that he used a "T" on the handle end of it where yours has an end cap, to make it easier to fill and expel the water. Having used one of his in a water gun fight while floating down the river in a canoe, when some guy thought he was going to ambush us with a super-soaker, he was in for a huge surprise when I unloaded on him. What great fun! Thanks for this tutorial. I enjoyed it very much.

Might I suggest using white grease for the lubricant rather than vaseline? White grease has been used on car doors to keep them operating easily and quietly for many years. I don't know if this will work or not because I've never tried it, just a suggestion. I understand the conflict of using Vaseline and latex. I think that's the warning on the side of a box of condoms.

danpritts (author)bogie71292014-07-15

There's a clear silicone grease for car windows that might work well. I used vaseline since I had it handy. I don't think the o-rings I used were natural rubber, I bet they will be fine. If not they were cheap enough. :)

seamster (author)bogie71292014-06-20

You're welcome! Glad to share. I'll have to take a look at white grease.

Thanks for the thoughtful comment.

LYHTSPD (author)2014-07-15

I made one as a trial and plan on making the other 5. I had a hard time finding the right 3/4" fitting so I ended up doing what another user did. I could not find the adapter that had the round collar in the plumbing section. I did find it in the electrical conduit section. It is a 3/4" box bushing for nmc. I then used a 1/2" slip in pvc plug to seal the end.

Something else I had an issue with it not knowing how far too pull out the plunger tube. I used the purple pvc primer to mark a stop ring about 2" wide right next to the oring assembly. This lets the kids (and me) know when to stop pulling on the plunger rod before you pull the assembly apart.

Thanks to the OP for this fun ible!

seamster (author)LYHTSPD2014-07-15

You're welcome! Glad you were able to make one. And good work-around for the plug piece. I thought that area would require a little tweaking for most people, depending on what they can find in their local stores.

Thanks for the great comment and helpful tips!

thegannclann (author)2014-07-04


seamster (author)thegannclann2014-07-04

Excellent, that will help a lot of people. Thank you!

zacker (author)2014-06-27

cool... im thinking, make them from 3" and 4" tube with a 1/2" hole for the water to shoot you could put a fire out with them! lol Nice Job, thanks for showing how its done!

seamster (author)zacker2014-06-27

You're welcome! You could indeed put out a fire with that, or knock over a couple kids! Hmmm...

EmmettO (author)2014-06-17

I've built similar pvc guns, I was always worried about using petroleum jelly because I thought it might eat through the o rings. I tried mineral oil to limited success.

seamster (author)EmmettO2014-06-17

I had the same concern, but in the end I concluded it was still the best option. I have some lithium lubricant that's supposedly rubber-safe, but I wouldn't want my kids being sprayed with it, even in tiny amounts.

I tested these with some water based lubricant and it didn't work at all. I ended up just sticking with petroleum jelly, and figured I could replace the o-rings if/when they deteriorate.

jtalvy (author)2014-06-14

Nice job! I think I will make some for my nephews.

reddog77 (author)2014-06-13

Great idea! I would add a "T" connector on the end before the end cap, then you have a handle for easier operation.

jaret (author)2014-06-13

A cool idea would be cutting those large pool noodles and zip tying them on. Would make this project safer!

bogie7129 (author)2014-06-13

I had one of your older type water guns a few years ago. We went canoeing down the Blackwater River in northwest Florida one hot summer day and I took my water cannon along. As we rounded one bend in the river, there were a couple of baddies ahead lying in wait with their super soakers. They pointed them at us and starting trying to get us wet. I pulled my cannon out of the bottom of the canoe and let them have it. You can not imagine their surprise when I waylaid them using my water cannon. They were ready to throw their supersoakers in the trash can after I finished with them. What great fun we had, too.

As an aside, my brother who lives in Texas, made mine for me. He was using his on Lake Travis one day when some crybaby complained to a passing cop that he got soaked by some heathen with a water cannon. The officer took my brother's water gun away from him, saying it was a weapon, and that if he ever caught him using it again he'd arrest him for assault with a deadly weapon. Har de har har har. What a goober. Just so you understand there's goobers everywhere. Use of this type water gun should be judicious, be one your best behavior.

jgibso7 (author)2014-06-12

Very nice! I was wondering where the dental floss was going to fit in.... great use for it. I might try somthing like this with schedule 40 electical conduit. lots of differnt typs of fittings and connetors. you got my hamster wheel spinning...

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Bio: I got an old sewing machine when I was just a kid, and I've been hooked on making stuff ever since. My name is ... More »
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