DIY bubble-counter puzzle - The Planted Tank Forum
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post #1 of 4 (permalink) Old 01-31-2005, 04:51 PM Thread Starter
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DIY bubble-counter puzzle

I'm running DIY CO2 on my 30g.
Right now I'm just using 1 2L juice jug.
I run approx 4" of tubing to a check valve, and then directly into a Hafen ladder.

In order to avoid yeast-snot, I added a 500 ml bubble counter bottle.
Drilled 2 holes in the 500 ml cap.
Ran approx. 10" of tubing from the yeast bottle to below water surface in the bubble counter.
Then, out of the other hole the original segment of 4" tube/check valve/tube to ladder.
Pretty standard set-up.

The problem is, when I connect the bubble counter, no CO2 makes it to the ladder.
The yeast bottle is nice and foamy.
I can see bubbles in the bubble counter water - they rapidly multiply when I gently squeeze the yeast bottle.
I can see gas in the tube to the ladder, near the tank's water surface, but the gas level never gets down to the bottom of the ladder.
When I squeeze the bubble counter, I can make the gas go down the line and enter the ladder.

So there don't seem to be any obvious obstructions/leaks.
I siliconed around the tubes on the caps, to make sure there were no leaks, to no effect.

In order to get CO2 in my tank I pulled the counter and figured I'd just clean the periodic snot.

But can any of you venture any guesses why this is happening?
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post #2 of 4 (permalink) Old 01-31-2005, 05:33 PM
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I think you want to make the input to the bubble counter go only about one inch below the water line, then the output line is about 1 inch above the water line. the reasoning is that the pressure in the generator has to push down against the level of water in that bottle, then again inside the tank. So, keeping the input lines low in the counter and in the tank just adds unnecessary head pressure to the generator. Otherwise, the best guess is still leaks, try submerging the system in a bucket of water to see any leaks, after you reduce those input lines if it still doens't work.

PS, also be certain there is not any water in the line going to the fish tank, for the same reason. It doesn't take much water in the lines to add several inches of back pressure to the bottles. For that reason, it is wise to keep your generator and bubble counter on top of the tank until the unit is bubbling into the tank well. At the start, when there is some CO2 in the line but no real pressure or flow rate built up, the CO2 is so easily absorbed that the water will travel up the line. Once it is over the rim of the tank, gravity pulls it down, filling the line. That many inches of water is just too much for the generator to work against. So, inspect the line, and shake any bits of water back toward the tank.
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post #3 of 4 (permalink) Old 01-31-2005, 08:37 PM Thread Starter
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Thanks, anona.
It's the kind of thing that now that I have it running, it is easy to ignore until there's a huge honking ball of snot hanging out the bottom.

So, should I try to elevate the entire counter bottle as well? I've seen some setups where the counter is taped high on the generator bottle.
-Should I make the tube between the generator and counter as short as possible?
-Does it make a difference if it goes up and down a big arc betwqeen the generator and counter, as opposed to a shorter straighter path?
-Does it matter how high the water is in the counter bottle? I had the water up to a couple of inches from the top, with the line from the generator going all the way to the bottom, and the line to the tank just an inch or so through the cap.

This is too much like physics for my atrophied lawyer-brain to handle!
I think I need a nap!
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post #4 of 4 (permalink) Old 01-31-2005, 08:55 PM
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the only thing you really need to wrry about is where you have gas trying to push down against water. The line length is not an issue since a column of gas weighs nearly nothing, line length is only an issue as regards to losses through the line itself. So, keep it a short as in comfortable, but don't sacrifice a couple of inches that you need, leave some slack so you can move things as needed, or tape them together and have no slack at all, whatever works.

Taping the counter bottle? I found that if they were "together" it helped when I had to move them from the shelf below the tank to above the tank, which I always did before opening the generator bottle or the counter bottle. Just don't grab one and forget the other and yank it so hard the glue fails... been there, done that. I don't think it is an issue with relative liquid levels and the potential for siphoning between them, but I'm not sure.

Now the level of water *relative* to the input tube is the key to how much water the gas is pushing. I liked to have the counter bottle relatively full, so that there was more water there to absorb any nasty stuff traveling with the gas. But not more than about an inch above the input line. And I liked to have a few inches of empty space in the counter, so that if the tank should siphon, it would have a bit of room to fill before it got to the generator, or if the generator foamed, it has some room before it got to the tank. I eventually went to a 20 oz soda bottle as the counter and a 2 L juice bottle as the genearator, I think because I had the line between the two so short it was a problem and so changing to a taller bottle allowed me to keep the same cap and line assembly I had finally gotten leak-proof.
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