Pressurized PVC water gun

Hackaday’s [Caleb Kraft] has branded today “kiddie d-day” after seeing this PVC water gun follow close on the heals of the LEGO sniper rifle. This is a great summer project if you don’t mind letting the kids use the quick connect on your air compressor. It’s really just a ‘T’ made of PVC with two valves for air and water management and a soda bottle on the third leg as a reservoir. In the short clip after the break you can see that you don’t get a lot of shooting time out of each charge compared to the DIY Super Soaker, but this build is also a lot less complicated.

[Thanks Frogz]

Comments

  1. woutervddn says:

    muhahaaah! xD that’s one I just have to trie!

  2. Ideas_Man says:

    How about you have a bottle full of water coming off the bottom, with a tube to the bottom of that bottle connected to the nozzle valve to draw the water up. Then have another empty bottle coming off the top. The two are openly connected. More volume for compressed air would really improve that shooting time per charge.

  3. Harvie.CZ says:

    what about exploding PET bottle destroying your eyes and recognizable parts of your face?

  4. djrussell says:

    “This is a great summer project if you don’t mind letting the kids use the quick connect on your air compressor.”

    this doesn’t use an air compressor. it’s a quick connect to the water hose.

  5. barry99705 says:

    @Harvie.CZ

    If the water pressure at your house it that high, you have bigger things to worry about. Like your water heater exploding, faucets failing, or the shower stripping all the hair off your head.

  6. cgmark says:

    Your home water pressure doesn’t have to be high for this to work. Go outside and turn on the hose and cap the end, now stab the hose with an ice pick and watch what happens.

  7. cgmark says:

    Home water pressure is around 30-50psi max and a soda bottle can withstand about 100psi so nobody is likely to be anywhere near the limits of busting the bottle.

  8. eric says:

    A physics professor told our class that plastic soda bottles can withstand about 1,000 psi before rupture. This was back in ’93, so things might have changed since then.

  9. j9 says:

    re PET bottles exploding… there’s plenty of places on the Internet (including a NASA site) showing people building air/water rockets out of those things. They are generally pumped up to 80 PSI. http://dogrocket.home.mindspring.com/WaterRockets/index.html

  10. Jack says:

    I have personally taken a two liter PET bottle up to about 180 PSI without it breaking. My pump wouldn’t go any higher. Even if the bottle did rupture, it wouldn’t produce shrapnel and if the water came out of the rupture, it would be at the same pressure as your water line. Most of us willing stand under a shower every day. The pressure is safe.

  11. octel says:

    @Harvie.CZ

    If the bottle is mostly full of water, it’s not going to explode but rather crack and leak out.

    Water isn’t compressible, but air is and will act like a spring:

    If you pump a bottle full of air, it will probably explode and send shrapnel everywhere since the air compresses inside. However, pumping a bottle full of water is relatively safe because the only springiness in the system comes from the plastic stretching.

    One of the applications of this is used in making 2-stroke exhaust pipes in a process called hydroforming. You sandwich two pieces of thin sheet metal, weld them, add a water connector, and pump the assembly full of water. The vessel fills with water and deforms into a metal “bag”. Cut off the ends and you have an exhaust pipe!

    A single pinhole leak in a system full of water will safely depressurize everything.

    Example:
    http://i49.tinypic.com/20jfx9e.jpg
    http://i50.tinypic.com/2j137m0.jpg
    http://i45.tinypic.com/jii7wi.jpg

  12. nobody says:

    The lack of complexity to this project makes it’s notability a sad commentary on the decline of the education system.

    Air compressor+garden hose=squirt gun? This is a 3rd grade level science demonstration. Not a hack.

  13. Jordan says:

    Even if the bottles are rated higher than the pressure applied, it would still be prudent to use eye protection while operating this apparatus.

    My general rule of thumb isn’t to go off of the materials limits, but instead go off of what the catastrophic failure would do to me. Since you can’t guarantee that there are no manufacturing defects in the bottle, I would definitely recommend some precautions. A bottle rupturing under that much pressure would be painful, and have the potential for permanent eye damage.

  14. Chuckt says:

    We’ve used pressure washers at work and the more powerful ones are like a nail and can make you bleed.

    Even the regular super soakers carry a warning.

    Just one question guys, have you ever heard of just using a hose?

  15. tim says:

    you only have on shoot, than refill.
    not enough for fiting against cats attack

  16. Jeff says:

    They should hook this up to that autonomous sentry gun system http://www.paintballsentry.com to keep Jehovah’s witnesses off my lawn

  17. octel says:

    @Chuckt
    super soakers carry a warning because americans love lawsuits

    it has nothing to do with actual safety

  18. As a kid we always had something like this behind our kid-vehicles. It was an expansion tank (from a central house-heating) with the valve of a bicycle pump. That way we had a manure tank of water running behind our mini-tractor. Was pretty awesome back then!

  19. Oh, good !
    I made one of those some years ago. I pumped up with a bike pump :)

    7Bars of pressure. You can best take those big coke bottles with 2mm wide plastic. Very resistant (until it explodes^^)

  20. PET is a nice material to work with really. A hair drier can shrink it enough. Good thing this reminded me of trying to make better seals by melting, i’d fogotten about it.

  21. strider_mt2k says:

    -not to mention that it’ll totally back up into the mains and kill some innocent plumber…

  22. TheShiningHalf says:

    Just wrap the bottle thing in duct tape. No shrapnel, no problem.

  23. jake says:

    @strider_mt2k:
    Thanks for the laugh. That made my day.

  24. Cynic says:

    *follow close on the heals
    The phrase is “hot on the heels of” as in, the backs of your feet.

  25. Fuggy says:

    ok please please please dont let the kiddies loose on the air compresser! please!! have you ever seen a pop bottle tear apart up high pressure!

  26. Steve says:

    The repeated pressurizing and depressurizing of the two liter bottle causes the plastic to fatigue. I have had more than one 2L bottle explode when filling it up with a hose.

  27. Milton says:

    Don’t you mean on the “heels”?

  28. cgmark says:

    This article is a good example of people that do not READ . There is no air compressor involved !
    The only reason the air compressor quick connect is used is to make attaching and detaching the gun from the WATER hose faster. It is totally powered by the water pressure of your home.

    About the bottle exploding – cannot happen unless you have seriously high , 150psi+ water pressure at home, which would blow every fitting in a normal home. PET bottles are pressure tested before being filled at 150PSI. They have to be because CO2 separates from liquid easier at room temperature than when cold. Someone dropping a 2 liter in a store causes pressures upwards of 100PSI inside the bottle. Stores would protest if every time a customer dropped one it exploded.

  29. Acyrons says:

    I had to try this here is my take on it. Mine is at 100psi tho.

  30. Acyrons says:

  31. jorjor says:

    Regarding 1000psi pop bottles…um, no. I had heard 180 psi max, but…
    I’ve done enough destructive testing of pressurized 2 liter pop bottles to know that:
    1) repeated pressurization will stretch and weaken the plastic, so that
    2) they will produce a deafening ‘explosion’ at 120psi.
    I pressurized one in an Army canvas duffle bag, for example, and when it exploded at 125psi it ripped large holes in the thick canvas, and made our ears ring for half an hour.
    Also, nicks or scratches in the plastic will seriously decrease max pressure and bottle life. *Absolutely* wear eye protection–both gunner and victim. For the purposes of making a portable water gun, you probably would be quite happy with a max pressure of say 45psi, which stuffs about 6 liters of air volume into a 2 liter bottle. If you use one bottle for water and one for air, you’d be able to move 2 liters of water with a little headroom left over. Please be smart, start small, and work up to a safe maximum. At the risk of being a wet blanket 8), think about the design parameters for hand-pressurized Super Soakers and go up just a bit from there.

  32. Frac says:

    You could build a quick release system that let you pre-charge 600ml bottles (the smaller ones). Your gun could then take the bottles like “clips”.

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