Introduction: Backyard Dunk Tank

Picture of Backyard Dunk Tank

OK, so you’re trying to plan some fun summer activities with friends and family and what is one thing that is always a bit hit at outdoor parties and cookouts? A dunk tank!! The problem is that there is never one around when you need it, and if it is around then you have to haul it in place, fill it with hundreds of gallons of water, then get dunked in water that is full of who knows what after a while.

Well, I have a solution for you. It is portable, lightweight, sanitary, fun for all ages and uses 3-4 gallons of clean water per shot. All you need is a hose and a place to put it.

There are other styles of these tanks around that require power (which may pose a danger around a water feature) or components which are prone to failure, but this design is, basically….wait for it…..a giant toilet!! It uses the same components found in your home toilet of a flapper valve and a float valve, that’s it! Let get this thing made!

By the way, this looks like a complicated build but it goes together very easy, I just try to be very detailed (read verbose) when I lay out the steps.

Step 1: Tools and Materials

Picture of Tools and Materials

Tools are pretty basic:

  • Chop saw or hack saw to cut PVC pipe
  • Drill with bits
  • Basic hand tools

Material – most of the items can be picked up at your local hardware store but I did include some online sources for some of the components:

Step 2: The Flapper

Picture of The Flapper

The first step is to make the mount for the flapper valve. There are a couple of different ways to make the mount. I was fortunate to have access to a 3D printer for this piece, but if I didn’t, I would have taken a piece of 1/8” thick aluminum stock bent into a U-channel and drilled to accept the cross rod. The bottom of the mount needs to be pretty flat to facilitate mounting it to the bucket. Fortunately, though, my son had a drafting class at school and offered to draw and print the mount for me. It is 1/8” thick, 1” wide and 2” tall. The holes are ¼” (same size as the fiberglass rod) and drilled 3/4” from the bottom. The larger third side was glued on later to restrict the movement of the flapper so it wouldn’t open too far.

Next, cut the fiberglass rod so it extends past the sides of the mount around 1”on each side. A note on cutting fiberglass; I found it helpful to wrap the cut area with masking tape before the cut and apply super glue to the ends immediately after cutting to prevent fraying. You may also want to wear a mask or keep the rod wet when cutting to reduce the possibility of inhaling fiberglass dust.

Insert the rod into the drilled holes and secure in place with the silicone sealant. Make sure the flapper can fit on the rod and operate freely. You might need to trim the corners of the flapper to allow free opening and closing of the valve.

Now you can drill a hole in the bottom center of the bucket that is slightly larger than the flapper seat ring hole and then attach the seat using silicone sealant. This part is optional if you don’t have the seat ring but highly recommended to get a good seal from the flapper valve. Once the silicone has cured, install the flapper on the mount and line it up over the drain hole. Use more silicone sealant to secure the mount and let it all sit until the silicone is fully cured. Remove the chain that comes with the flapper.

Step 3: The Float Valve

Picture of The Float Valve

The products I mentioned in the material section for the float valve fit very well inside a 5 gallon bucket but you can certainly use and adapt whatever you may have around from a plumbing repair or what have you. My main concern was to have the refill take less than one minute to keep the dunking activities moving along and this valve is rated for 12.5 GPM @ 60 psi, which, at typical household pressure, is about 6 GPM. It puts about 4 gallons in the bucket in less than 45 seconds.

Locate an area about 1-1/2” below the top of the 5 gallon bucket to mount the valve. In my case this was right at a ridge in the bucket so a little trimming was in order to make the area flat enough to drill out the 7/8” hole needed for the valve. Connect the 3” rod and float ball to the valve and mount through the hole with the valve nut. The final connection is the double female hose connector so you can hook up the garden hose when ready. Test the ball float for free movement in the bucket, sometimes you may have to rotate it to the side a little.

Step 4: The Frame

Picture of The Frame

The frame is basically a large rectangular box with a couple

of extra beams across the top to support the bucket.

We’ll start with a cut list for the 2” PVC pipe:

  • 4 ea - 60” pieces, basically cut 2 of the 10’ lengths in half
  • 7 ea – 30” pieces
  • 2 ea – 13-1/2” pieces
  • 4 ea – 10” pieces
  • 2 ea – 6” pieces
  • 2 ea – 1-1/2” pieces
  • 1 piece the height of your bucket + 4”

First make the bottom frame by gluing 4 of the 30” pieces into a square using 4 of the 90 degree elbows with side outlets (I will call these pieces corner elbows) making sure everything is square and level.

Next glue two corner elbows to each end of another 30” piece, again, making sure the corner elbows are square to each other.

Attach the 13-1/2” pieces to the legs of a tee then the last two corner elbows to the end of that assembly so the regular tee will be standing up when assembled, square and level.

Now glue two of the regular tees to each end of the last two 30” pieces (call these center struts), you know…square and level.

Connect the center struts together with the two 6” pieces then glue the 10” pieces to the last leg of the tees.

The final step of the top assembly it to connect the 30” pieces with corner elbows to the outside of the 10” pieces making sure it is all square and level. I know I am repeating this but it is very important that everything lines up since not all of the pipes in the frame will be glued and you want as little stress on the joints as possible.

Now you just need to put a 60” piece in each of the bottom corner elbows and put the top assembly on the top of the 60” pieces. I did not glue the 60” pieces on either end so I could disassemble the frame for storage but I did secure the pieces into the corner elbows with self tapping screws.

I cut down a scrap piece of plywood the length and width of the center strut section to add strength and stability when the weight of the bucket is added. Drill a 2” hole in the direct center of the board then use screws to attach it to the top of the frame.

Step 5: The Trigger

Picture of The Trigger

Now the build gets a little trickier and attention must be paid to sequence of gluing the pieces together to ensure proper operation. Most measurements will not be given because much of the alignment depends on the size of the bucket you are using.

First take the 2” cross tee and glue the 1-1/2” pieces of 2” pipe into opposite ends of the tee. Clean any extra glue immediately since this area must remain clean and smooth.

Measure across the width of the cross tee and the inside lip of the 1-1/2” coupling and 45 degree elbow. Add these up and cut a piece of 1-1/2” to this length +1/4”. Glue this piece to the 45 degree elbow and slide it through the cross tee and 2” pieces you previously glued. The 1-1/2” piece should fit inside the 2” pipe pieces with a little room to spare. Now glue the 1-1/2” coupling to the other end of the pipe you slipped through. This will form a nice hinge that will not slip out of the cross tee.

Place the 5 gallon bucket on the plywood board so the flapper valve is right over the hole in the plywood. I installed a couple of screws on the outside of the bucket to keep it from sliding around. Take the “bucket high” piece of 2” pipe and glue it into the vertical tee on the top assembly then glue the cross tee hinge on the top of it so the 1-1/2” coupling is facing the hole in the bucket. Cut a piece of 1-1/2” PVC approximately 42” long, or as long as you want it for the target arm. Glue this into the 45 degree elbow so it hangs down on the side of the top assembly.

Trigger edit August 2017

Measure from the inner lip of the coupling to the hole in the bucket and cut a piece of 1-1/2” PVC to this length and glue it to the coupling, then glue the 90 degree elbow to the end making sure it is facing to the rear. Next cut a piece of 1-1/2” PVC approximately 10” and glue it to the 90 degree elbow facing to the rear.

Step 6: Putting It All Together

Picture of Putting It All Together

Cut a 10” diameter circle from some plywood for the target and attach it to the bottom end of the 45 degree pipe. My initial attempt was to use 2 screws but that proved inadequate so I would recommend two 1-1/2” pipe clamps bolted to the wood.

Trigger edit August 2017

Install screw eyes to the bottom of the rear facing PVC and the top back of the bucket. Tie off a piece of string or heavy fishing line to the flapper and route it through the eye on the bucket and connect it to the eye on the PVC.

At this point I put a piece of surgical rubber tubing to relieve stress by tying it off to the eye on the PVC and a second eye on the frame. This will keep the arm from going to far in the event of a hard hit which would pull the flapper from it's mount. Make sure the flapper opens when the target is moved to the rear.

Two other modifications I made were to put a ratchet strap over the top of the bucket for safety and hook a few fishing bobbers to the line right above the flapper. The force of the water exiting the flapper was causing it to close too soon so the bobbers help keep it open until the bucket is empty.

Step 7: Getting Wet!!

Picture of Getting Wet!!

Time to put the tank in a level place, find a chair to put under it and connect the hose. Here is where my evil side creeps out, though, as I prefer to connect the hose to my lawn irrigation well so the water is a nice 55 degrees rather than the 65-70 degree tap water. Believe me when I tell you, the first shot from this will take your breath away!! Saves on the water bill also.

I use 1lb beanbags I made for playing cornhole as the projectiles. They seem to have the perfect weight to trigger the tank and are light enough so the small kids can participate with no problems.

Thanks for suffering through this intolerably long Instructable, I hope you decide to make this project and enjoy hours of cool fun with friends and family!

As always, please contact me with any questions and feedback is welcome.


A2MattWeber made it! (author)2017-08-20

Thanks for the instructable! We made this for a circus/carnival-themed birthday party this weekend. We used your new trigger arrangement and it worked just great! It dumps a very satisfying amount of water when triggered. Yea!

For the ball, we used a half football thing that was a decent weight, soft, and, due to its shape, didn't roll away too far:

I should also mention that I found this bracket online:

It worked perfectly to hold the flapper in place (since I couldn't 3-d print one). I did have to drill a couple of holes in it and place a rod through it to hold the flapper in place but that was easy.

Thanks again for a great project!

IamGutter (author)A2MattWeber2017-08-29

Fantastic build! Glad you enjoyed it and thanks for posting the links to your parts. The flapper holder looks fantastic, I may have to get one for the next one I build since I don't have access to a 3D printer any more.

MelodyT15 made it! (author)2017-08-26

Thank you for your instructions. We got it done and it was the hit of the party. Thank you!!!

IamGutter (author)MelodyT152017-08-29

I'm so glad you got it done in time and every enjoyed it!! I love the extra touches of the shaped target and the decorated bucket -- it looks awesome!! Thanks for sharing your success!

IamGutter (author)2017-08-10

Sections 5 and 6 above have been edited to show an updated trigger design. Enjoy!

Kmcglynn1 (author)2017-08-06

Excellent instructable! How do you transport the completed assembly, especially with the upper section being so tall and wide, since it is all glued together? Could you use a bolt through the tee on the left through the trigger arm upright and/or the long tube off of the 45 degree coupling instead of gluing them?

IamGutter (author)Kmcglynn12017-08-10

Hi there. That is exactly what I do! The trigger is not glued into the tee that holds it upright, I use 8 self tapping screws to hold it in place. The units breaks down pretty well for transport, basically the top frame, bottom frame (both of those sections are glued) then the four vertical uprights and the trigger arm. Believe me, mine travels a lot!!

Jtdpr made it! (author)2017-07-22

I made it but made some changes. Used wood instead of PVC for cost and changed the trigger mechanism. I used 4 strings instead. 2 attached to the chain and 2 attached to a screw on the top. If you pull the wrong string it dumps on you. Even though I changed many things I promise this was based on your design. Thanks for the plans.

debbielockwood made it! (author)2017-07-05

So we built the dunk tank and used it for the 4th of July to raise some money for a ministry at our church. We had a little bit of trouble with the trigger. It was hard to hit it hard enough to trigger the water release. We eventually got it to work but it was still hard for a younger a thrower to release the water. So we added a cheater rope to the top so that it was hit we could pull the rope and release the water. We have got it figured out how to fix it for the next use. Here are a couple of photos of the booth in use

IamGutter (author)debbielockwood2017-07-06

Great photos!! Our tank was out on the 4th as well and was a big hit as always. I can send you some photos of an easy modification to the trigger that makes it much better. What I really need to do is update the Instructable!!

Thanks again for building this and glad you enjoyed it!

canarycream (author)2017-05-28

Sorry about the video but here is a still from it. The kids think it is a hoot! Thanks for doing this instructable

canarycream made it! (author)2017-05-27

I made it. It is still in the tweaking stage though. But so far we love it!

IamGutter (author)canarycream2017-05-28

Excellent!! Can't seem to get the video open, but thanks for letting me know about your build. Hope you enjoy it all summer!!

Eboneejoyce (author)2017-05-28

Pics from the carnival. Everyone had a great time!!!! It will not let me upload the video

IamGutter (author)Eboneejoyce2017-05-28

Glad everyone had fun, looks like it dumps out lots of water!! Thanks for the pics!!!

Eboneejoyce (author)2017-05-12

I need help please. I have finished this setup and it's great! The kids as well as the adults love it. I added a couple of side pipes because I did not use 2" pipe. I used material I had on hand. The only problem is.....sometimes when the triggers arm is hit it goes completely around 360 degrees and continues to break the chain from the flap. My arm is just ran through the side of the bucket coming off the tee. I have a carnival coming up and need to get it fixed. Any help will be so greatly appreciated.

Eboneejoyce (author)Eboneejoyce2017-05-25

Thank you so very much. This info came in just in time. Our carnival is coming up in 2 days. I was able to get everything fixed and it works perfect...I will post pics of it. I had to add PVC pipe to the arm and put the rubber piece on it. Thanks a million!!!!!!

IamGutter (author)Eboneejoyce2017-05-15

Sorry for the delay in responding, I didn't get a notification of a new comment.

I like Phillips idea of a second bungee cord to take the extra weight of a hard throw. Another possibility might be to put some more resistance at the tee where the arm goes through, maybe a bungee wrapped in a cross fashion so it contacts either side of the tee to slow the rotation.

I use a piece of rubber tubing inline to absorb the extra weight from a direct hit.

I would be interested in your final solution, please.

PhillipR37 (author)Eboneejoyce2017-05-13

Instead of chain, I used bungie cord rope. And I added a second piece of bungie cord connected to the PVC pipe for additional resistance in case someone hits the target really hard.

cflores291982 (author)2017-03-20

About how much does it cost to make one of these?

IamGutter (author)cflores2919822017-03-21

I have about $120 in materials in it, plus a few items I already had (plywood, plastic, tubing, etc.) I know you can get something pre-made and similar online for a little less, but this is much more heavy duty than anything you can order.

CreativeBlossom (author)2016-09-08


LCF2 made it! (author)2016-07-24

here is my second one that i have made these are way to much fun, this one is for my niece vac bible school coming up they will be a big hit you cant go wrong with kids and water lol.

Superbender made it! (author)2016-07-10

Again, fantastic instructable. I simplified the frame to an A-frame ladder and used the suggestions for improving the trigger from the comment section. Works great. Thanks for posting this great idea.

bntrow made it! (author)2016-07-07

My husband and a friend made this for our church's vacation bible school. We named it after our friend. The plexiglass front served two purposes: a place for the name and a shield to protect the victim from wild throws. Our friend had a lot of the fittings and the flush valve on hand. And, yes, he works at Ace hardware in the plumbing department.

IamGutter (author)bntrow2016-07-07

Looks great! Ours got a great deal of use last weekend, it is still a big hit on a hot day.

I like the double uprights on the trigger arm, looks really sturdy!

Thanks for checking it out and building one!

LCF2 made it! (author)2015-09-26

ok I made mine I did a few things different on my trigger arm coming off the 2 inch tee to a 11/2" tee then a reducer to 1" for my arm. drill a 1"hole in top of bucket ran my pipe inside the bucket up at the top this shorten the arms and less weight it works prefect

Lone Ninja (author)LCF22016-04-17

Awesome upgrade. I plan on making one myself and I will use your trigger mechanism improvements!

LCF2 (author)Lone Ninja2016-04-17

yea i found out too also that when yu come off the 2' is too go to a 1 1/4 " inch the one inch slides thru it prefect so when i build another that my plan go to 11/4 on my trigger come out of the tee reduced down to 11/4 inch then too 1".

mferny (author)LCF22016-06-29

This is great. I have started to build this but still don't understand the trigger. Where is the string run and how does it rotate in order to pull the flapper?

LCF2 (author)Lone Ninja2016-04-17

that great but i have found out that you can actually come out of the 2 inch to a 11/4 tee then run one inch thru it fit precept

Bobby PamB (author)LCF22016-03-22

Could you Please share this with me how you Built this going to make for school carnival thank you..

LCF2 (author)Bobby PamB2016-04-17

do you still need help bob i build everything except the flush valve and the trigger just like he said i only change it up on the trigger part i got a cattle plastic fill valve from eBay for like 5 dollar then you can go several differ ways on the flush i bought one that you just use the sticky gasket that came with it it was one piece but now i cant seem to found them anymore if i were to build another i just buy a flush from ebay Fluidmaster Inc. 507A Universal 2” Toilet Flush Valve & Flapper it 7.95 just cut the pipe off mount it in the bottom center bingo you be in business.just make sure that the hit arm is down then glue your pipe in that will pull the flush valve open when it is hit .in other words when all is resting that pipe need to be leaning back so as to when it is hit it will pull the flush valve open soaking the awaiting happy kid or adult.

IamGutter (author)LCF22015-09-26

That is sweet! I am making a modification to mine for next year based on comments below that will shorten the arm as well. Hope it is still warm enough were you live to enjoy it yet this year. Thanks for making one and sharing your success!!

LCF2 (author)IamGutter2015-09-26

I hate to bother you with this but I wanted you to see the set up on mine .its worked out very good again thank you so much fpr posting how to make this its save me around 150 dollar ovr those on ebay they are no were as strong as this one .

IamGutter (author)LCF22015-09-26

That is fantastic!! Glad you liked the idea, hope you have as much fun with yours as we do with ours!! :)

Superbender (author)2016-06-18

This is an awesome dunk tank. I am in the process of building one right now for my son's birthday party. The plan is to use my A-frame ladder as the frame and just have the bucket and (improved) trigger attached to a piece of wood that rests on the steps of the ladder. I'll be raising the ladder to the appropriate size and voila. Hope it will reduce the cost for the pvc a bit.

szachta68 (author)2016-05-18

We are making this for our kids school. Everything works great except.....

We purchased the tank mounted fill valve you recommended. When everything is hooked up, the weight of the hose causes the fill valve to turn. This causes the float ball to either touch the bucket wall or make contact with the flapper. We have even tried to zip tie the hose to the pvc frame. I have tried silicone but that didn't work either.

Do you have any suggestions on how to keep the float valve from turning?


IamGutter (author)szachta682016-05-18

Hi there. Thanks for taking the time and effort to make the dunk tank, I hope the kids really enjoy it, assuming we can fix your problem!! I am at work right now so I don't have my tank in front of me, this is all from memory.

As I recall, there should have been 2 gaskets that fit on the stem of the fill valve and go on either side (inside and outside) of the bucket. You can see the inside one (white) in the Step 3 picture. Once those were on and the outside nut securely tightened, the valve stayed in place pretty well. I could turn it slightly to adjust it and avoid the float touching things as you describe, but it didn't move on it's own. I am very surprised that using zip ties on the hose didn't solve the problem, as I also used ties (several of them) to attach the hose to the frame; you can see one in the Step 7 picture.

Since you tried using silicone, I will assume that you don't have the stem gaskets, so you could try using garden hose gaskets ( and really tighten up the outside nut along with zip ties in at least 2 locations on the vertical PVC frame piece. This should hold the fill valve in position. Hope this helps! If not, hit me up again and we will try something else!

szachta68 (author)IamGutter2016-05-18

Our valve only came with 1 white gasket. We used 2 (replaced the white gasket) hose gaskets. The valve tightened up and does not turn. We tested it and everything works great. The kids will love it. Thanks

IamGutter (author)szachta682016-05-18

Fantastic!! Great to hear that you got it solved. Would love to see a picture or two of the final build, if you could. Thank you!!

szachta68 made it! (author)IamGutter2016-05-26

The dunk tank worked great. Well, at least until a couple kids got too rough with the trigger arm and broke the bracket away from the bottom. Nothing we can't fix. Here is a picture of our school principal getting soaked.

IamGutter (author)szachta682016-05-27

Fantastic shot!! That is the nice thing about working with PVC, it is usually easy to fix. Hope everyone enjoyed it; I will be breaking mine out this weekend for a neighborhood cookout. Thanks for taking the time to make this and share your story!

ayedunno2002 (author)2016-05-07

Where did you purchase most of the pvc fittings from? Specifically the 2" elbow with an outlet.
Where we live they are proving to be not available in most retailers or mom and pop hardware stores.
We were hoping to build one this weekend for a Relay Recess at our kids elementary school.

IamGutter (author)ayedunno20022016-05-07

I bought most of the PVC fittings online; I also could not find what I needed locally. I believe it was buy I can't locate my receipt email, it was over a year ago that I built this. Sorry I couldn't be more helpful.

SarahA95 (author)2016-04-06

This is indeed a much more sanitary way to do a dunk tank. More than that, it is probably a lot cheaper too because your not wasting all that water. I should talk to my sister to see if we could get one for my nephews birthday. He would probably love to have us all get water dunked onto us with this!

Midnightallie (author)2016-03-17

How much did all of the materials


IamGutter (author)Midnightallie2016-03-17

I have about $120 in materials in it, plus a few items I already had (plywood, plastic, tubing, etc.) I know you can get something pre-made and similar online for a little less, but this is much more heavy duty than anything you can order.

Fionaussie (author)2015-10-05

Thx for sharing! How fun!!

lime3D (author)2015-07-27

This is great. I'll keep this in mind for a future project. I'm just a bit confused about the vertical upright on the trigger mechanism.

I understand that when the trigger is hit, the top of the upright rotates forward, with the string or cord passing through the screw eyes to pull the cord vertically.

Would this work by simply turning the PVC "upright" 90 degrees to make it horizontal? When it rotates, wouldn't it would rotate up, pulling the cord? (eliminating the need for the wood post)

About This Instructable




Bio: I retired from the USAF in 2005 and now work for a local government as a project manager. I live in a fantastic neighborhood that ... More »
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