Easy Water Pressure

Build a homemade water gun or water balloon launcher and tell us about it.
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weird weird dude
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Easy Water Pressure

Post by weird weird dude » Sun May 14, 2006 12:05 pm

I was just thinking about another way to get water pressure. If you strung up a
back-pack water supply in a tree you could get easy water pressure.Just like a water tower. But I am not sure if it would work so if anyone would care to try it,
feel free.
Last edited by weird weird dude on Sun May 14, 2006 12:06 pm, edited 1 time in total.
Reason: spelling
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SSCBen
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Post by SSCBen » Sun May 14, 2006 1:05 pm

Welcome to Super Soaker Central.

This wouldn't work at all. There is one big misconception here: water does not pressurize in this situation, rather, gravity just makes the water flow. Water is incompressible for our purposes. Height does determine the potential energy due to gravity, but the backpack would only need to be higher than the gun for the water to flow.

Now, in an actual water tower, the weight of the water pushes the water out at a higher speed. Even more interesting are old mining techniques which used heavy weights on top of a seal to push water out. As you can see, the technique was extremely effective and powerful, in fact, it was far too effective for mining and caused much damage to the environment.

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joannaardway
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Post by joannaardway » Sun May 14, 2006 5:25 pm

Very simple calculation:

For each 10 m of water above the tap/end of hose, you have 1 bar of pressure.

As, in a tree I would expect 3m at most, you would get .3 bar pressure. Not enough to do anything with.

Mains water supplies have to be at least 1 bar pressure (at least here in the UK) but .3 bar is really not good. It would take huge effort to lift any reasonable amount of water those 3 metres, so I suggest a air tight tank, a pump and a tap if you have to have pressure in the field.
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Silence
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Post by Silence » Sun May 14, 2006 7:15 pm

Welcome to SSC.

@ weird weird dude: The question is, do you want to use this to pressurize a reservoir, or do you just want to use it to fill a tank? The idea, in its current form, is impractical in both applications.

As everybody else has stated, there isn't nearly enough pressure to get a reasonable PSI in a homemade soaker or in a QFD; in fact, if not for check valves, the water would flow up out of the PC and into the elevated tank! If you're going to spend energy, don't use it to lift a heavy tank of water (which would be pretty hard, as it is); use it to pressurize a filling/pressure station.

For simply filling a tank or reservoir, Ben is correct yet again; you will have too much elevation to make this practical. What's the point of lifting a 50-pound tank to a great elevation when you can just pour water into your soaker while it's on the ground?

And still, of course, you might be thinking of a completely different application...in which case I'm all ears :cool: .

weird weird dude
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Joined: Fri May 12, 2006 12:06 pm

Post by weird weird dude » Sun May 14, 2006 8:19 pm

It sounds like if I where to try it, it would be labor intensive. But, would it make it easier to pump, thus more pressure in the end? Sorry I am a little bad at knowing this kind of stuff if I am wrong. I guess this won't work with most of us but if you had a gun to big for you, it at least could be pumped easily, I guess that it would be immobile, but with a pistol, it would be a way to defend a base or hill.
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Silence
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Post by Silence » Sun May 14, 2006 8:28 pm

No, it still wouldn't be too practical. If you're trying to pump more water into a PC that already has 100 PSI in it, then a tiny bit of extra pressure at the bottom of your elevated tank won't help too much--and it definitely won't be worth lifting that gigantic thing. In addition, as you use up more and more of that water, the pressure will go down. If you're going to be pumping at one place, you might as well rig up some QFD device using a hose if you want help in pressurizing.

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