10 replies to this topic

[BMM]

I'm working on a formicarium for my Tetramorium colony and was trying to figure out a hydration system that would last a little while without needing to be refilled. I tinkered around a bit and settled on using a small plastic container as a sort of water tower. It's about 1" in diameter and 1 1/2" tall and has a hole at the base to connect it to the tubing. My plan was pack some cotton into the tubing, but after testing it there was a very slow leak. I tried using plug with a small hole in it as an alternative, but the results was pretty much the same. I understand why it isn't working, but I'm a little lost in terms of possible solutions. I know several people here have designed their own water towers and water reservoirs, so I was hoping someone could give me some advice on how to fix this.

[dspdrew]

If any water tank you use releases water from the bottom, it will need to be air tight, or the water will flow until the tank is empty, no matter how much you try to slow it down.

[T.C.]

I was gonna do something like this for a water tower once, only obviously smaller and with a screen mesh over the top.

[BMM]

If any water tank you use releases water from the bottom, it will need to be air tight, or the water will flow until the tank is empty, no matter how much you try to slow it down.

 

This part I understand, but where I'm stuck is whether "air tight" can be achieved with cotton or any other porous material. I'd like the colony to have access to a wet surface, but obviously any leaking can be disastrous.

[dspdrew]

That's like trying to make a mesh fish tank.

[BMM]

That wasn't quite what I was getting at. The standard test tube setup, just as an example, allows the water to soak the cotton without leaking out. I'm making educated guesses, but I see two differences that are probably at play here.

 

The first is saturation. In a test tube, air can only enter through the cotton, so once it's soaked there's no flow of air. That creates enough of a seal to hold the water in place. My water tower, in order to be refilled, has to have an opening. I can use a cap to seal it, but I can't be certain that it'll be air tight. Also, I expect putting the cap on will cause enough compression to force some water through the cotton initially.

 

The other is pressure due to gravity. Because the opening is at the bottom, downward pressure is going to force the water out of the connector hole. Ideally I want the water to move via capillary action and not due to gravity. Cotton seems to be slightly too porous overcome that pressure, but I'm not really aware of any good alternatives. I'm shooting to keep a gravity fed system, as it takes up very little space and doesn't require any complex arrangements to facilitate wicking. 

[dspdrew]

You are right. The test tube setup is sealed (of course excluding where the water is supposed to escape). This creates a relatively higher pressure outside the tube helping to keep the water in. The skin on water is only strong enough to hold so much weight before it distorts to the point of allowing air to leak in and the water to drain out. The cotton adds to the skin of the water allowing for a much larger amount of surface area to seal the tube off. As the water on the surface evaporates, it very slowly allows small amounts of air in, pushing more water out in the process, saturating the cotton and sealing the tube again.

 

Your problem is the same one i tried to over come when trying to design fixed or mounted liquid feeders and hydration tanks. Not only are you having to rely on a plug or cap to keep it sealed, you also have a problem of everything draining out when you go to refill it.

 

Not sure if you noticed, but almost every formicarium I design has a hydration system that lasts months. The easiest way is to avoid all the pressure regulated system problems, is to just use wicking/capillary action. The only drawback to this is it requires a water tank lower than the nest, adding to the total height of the formicarium. I do have one design that does use a pressure regulated tank, but it's removable, avoiding the filling problem.

[sgheaton]

Atmospheric Pressure? 

What is it?

[BMM]

You are right. The test tube setup is sealed (of course excluding where the water is supposed to escape). This creates a relatively higher pressure outside the tube helping to keep the water in. The skin on water is only strong enough to hold so much weight before it distorts to the point of allowing air to leak in and the water to drain out. The cotton adds to the skin of the water allowing for a much larger amount of surface area to seal the tube off. As the water on the surface evaporates, it very slowly allows small amounts of air in, pushing more water out in the process, saturating the cotton and sealing the tube again.

 

Your problem is the same one i tried to over come when trying to design fixed or mounted liquid feeders and hydration tanks. Not only are you having to rely on a plug or cap to keep it sealed, you also have a problem of everything draining out when you go to refill it.

 

Not sure if you noticed, but almost every formicarium I design has a hydration system that lasts months. The easiest way is to avoid all the pressure regulated system problems, is to just use wicking/capillary action. The only drawback to this is it requires a water tank lower than the nest, adding to the height of the entire formicarium. I do have one design that does use a pressure regulated tank, but it's removable, avoiding the filling problem.

I’m familiar with your R&D journals. Without them I don’t think I would have figured out as much as I have so far.

 

I was thinking a bit more on how to make this work and I may have come up with a feasible idea. It may be similar to the removable tank you mentioned. I’m going to create an air tight container and add a hole at the bottom for the tube to connect into. I’ll turn the container upside down and fill it up to just below the hole. Then I’ll attach it to the tubing, using a silicone grommet to make sure it’s air tight at the connection. After that I should be able to just twist the container back up and then the water will start soaking the cotton. If I’m think this through properly, the seal will create enough of a pressure difference to prevent the water from leaking out. To refill it I’d have to remove the container and repeat those steps. I’ll probably make a prototype tonight and see if it works as expected.

[BMM]

So I threw together a prototype and it worked quite well. No leaking whatsoever. However, after messing with it a bit, I think I can improve it. I managed to find an airtight cap, so I’m going to completely seal the top of the container and put the cap on the bottom. Then when I need to fill it, I can swivel it upside down, so the cap is facing up and the connector hole is at the top, remove the cap and fill it to just below the hole. When I reinsert the cap, the compression will only be able to force air out as the water will be below the hole. Then I can swivel it back up. Doing this won’t require me to remove the container each time.

[dspdrew]

That's where I have the cap on one of my water tanks, for the same reason.