Super Soaker Central

One thing I've found with dual reservoirs is that, unless you equal the amount of water in both, you'll end up eventually pulling air in with your water when you pump. In my homemade, I have to equal the water in the two tanks otherwise I'll end up spurting air and water when one runs out.

EDIT: see correction in next post.

aEx, that's a strange phenomenon. My best guess would have been that, as long as the barrel connecting the two chambers is always filled, the pressure will equalize and the water levels will remain the same. Maybe I'm missing some detail here. Or maybe the problem arises if you angle the soaker while shooting - water will pool in the lower tank.

Unfortunatly no progress yet...going through a major software rollout at work that has been taking up a lot of my time (I'm an IT guy). I will get around to it though soon.

I have to admit, my drawing isn't the most accurate nor is it the best, but it'll do...



Black equals plastic, blue is water, and yellow + orange equals low or high pressure, respectively. Imagine the two tanks are connected by their outlets.

In example 1, the two tanks are pressurized to the same pressure. Water doesn't flow between the two because of the pressure and the fact that they are sealed. When water is drawn out of them, one is left with no water, so the water is forced out in the left tank along with air from the right, creating a bad stream.

In example two, everything is fine. Water and pressure drops at the same time, no problem.

Now, in example 3, which is just a non-pressurized reservoir, is what I think eternal46845 had in mind, the tanks are open to the outside. Just like a U-shaped tube of water, the water levels equalize thanks to some form of pressure-force that I can't exactly remember right now. If there is a good connection between the two reservoir on the backpack of eternal's gun, then the problem shouldn't arise...

... I did have to correct myself, cause' I think I got a bit confused... but I know that, if the two tanks are closed and not open to the air, then the water wont equalize...

Pressure from gravity, which is all that exists under normal circumstances, equals rho*g*h, or 9.8*density*height. In a system like this, there's way more air pressure from compression than from the difference in height, so gravitational pressure isn't significant.

I understand what would happen should the tanks begin filled as in diagram 1. But I don't understand exactly how they could be filled unevenly. If you start with both empty (like in the last part of 2 or 3), then the water level should always be even after that.

Or maybe the water gun was tilted while being filled, used, or fired. If the water pooled in the wrong place at any of those times, and then the gun was positioned so that the water seal the air within each chamber, then you could have a few problems.

Well, the old way I had to fill my homemade was to turn the tanks upside down then drizzle watter in until no more would go in. Then I'd be in situation one.

That was, of course, before I started "pressure-filling" (that's what I call it)

I only stated this because, my old way of filling never let the water equalize unless I did it manually....but that's another story.

aEx155, I think the problem you're experiencing is due to uneven amounts of air in the chambers. If the amount of air in each chamber is uneven, the water level can be different but the pressure can be the same. Then water will have to flow less from one chamber and more from another to keep the pressure even. Weird stuff, but it's the only way something like that could happen.

The pressures have to be equal, so the second part of #1 is simply impossible. Put a pressure gauge in both and you'll see they drop evenly.

Well, it doesn't work like that for me. When I fill it up (old way), I end up with uneven water levels (#1). I pressurize it with the bottles upside down (is that it?) then flip the bottles over when I fire. One runs out before the other (at least, the first time I tried it) and I end up with air in the stream.

Pressurizing upside down might make uneven air levels, so that could be your problem.

One pressure chamber running out before the others can happen, most often when the water gun is angled and the water levels adjust accordingly. But that's not like this.

It should be easier to explain this situation if you could replicate it and get it on video, but I figure it's not too important.

Ben wrote:Pressurizing upside down might make uneven air levels, so that could be your problem.

One pressure chamber running out before the others can happen, most often when the water gun is angled and the water levels adjust accordingly. But that's not like this.

It should be easier to explain this situation if you could replicate it and get it on video, but I figure it's not too important.

Yeah, it's not that important. But I guess it would be an interesting thing to investigate...

I actually got some pictures and a video of it in action....unlike what you said, one runs out before the other, and yes, it is weird.