# Co2 tubing help



## Subtletanks91 (May 29, 2013)

One of my customers just came in today and gave me his fluval 20g co2 kit, a random diffuser which I'm replacing, and a full cartridge. 

I had some extra co2 tubing from when I bought my gla regulator and I cut off a piece to use for this one. The problem I'm having is that the tubing is so rigid when I hang the cartridge on the back of my fluval spec, and put the tubing on the diffuser and the regulater, it won't sit right on the tank, the tubing is making a u shape in the tank itself instead of sitting straight up and down like a normal tank. 

If I use airline will that be ok? Or is there co2 tubing that is more flexible than the one gla provided me with my regulator? I would like to be able to start using the co2 in this tank to counter the algae I've had since getting the finnex epoch. Yeah I know strong light small tank. But I wanted a carpeting plant and that's what I got it for. I've been using excel but it's not working the way co2 does. 

Any suggestins guys. Aside from its a waste of money etc etc. it's a small tank. I'm not spending 200 on a paintball set up for a 1.6 gallon tank.


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## Mark Allred (May 3, 2013)

I have just been using the standard clear tubing on a two tank setup for a year now. It is still soft and pliable.


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## Subtletanks91 (May 29, 2013)

Standard airline tubing?


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## Mark Allred (May 3, 2013)

Yes, just the standard clear vinyl tubing.


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## Darkblade48 (Jan 4, 2008)

I have used standard airline tubing and also silicone airline tubing. Both work.


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## Subtletanks91 (May 29, 2013)

Why does everyone say to use co2 resistant tubing then.


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## Mark Allred (May 3, 2013)

Internet parrots. 
Because some/most tubing is supposedly permeable to CO2, and you will see some gas loss through the tubing walls. I think it is a non-issue, given the very low pressures the tubing is being subjected to.
I see some places sell silicone tubing for CO2, but have read it is more perneable than the vinyl.


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## Darkblade48 (Jan 4, 2008)

Subtletanks91 said:


> Why does everyone say to use co2 resistant tubing then.


No particular reason. I have never advocated it. Some people assert that CO2 resistant tubing is less permeable to CO2 (which is true...) but the amount that is loss when using non-CO2 resistant tubing is essentially negligible.


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## etk300ex (May 1, 2013)

air line is just fine!


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## PlantedRich (Jul 21, 2010)

Co2 is pretty much like any liquid or gas in that it finds the easy way out. If you have to go out through the wall or go out through the end of a tube that is nearly open, most will go out the end. Airline for me.


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## DrGonzo (Apr 12, 2012)

If you still want to use the tubing you have use a heat gun, hair dryer, or even soak it in hot water to make it more pliable. When it cools it'll harden and stay put.


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## rdmustang1 (Oct 20, 2013)

I've read very detailed reports that standard tubing loses 20% of CO2. While CO2 is cheap my time to refill is not.

Could this be all made up? Sure, but to me the additional cost (basically $0) or effort (using a hair dryer to soften the tubing) is worth the peace of mind..


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## PlantedRich (Jul 21, 2010)

rdmustang1 said:


> I've read very detailed reports that standard tubing loses 20% of CO2. While CO2 is cheap my time to refill is not.
> 
> Could this be all made up? Sure, but to me the additional cost (basically $0) or effort (using a hair dryer to soften the tubing) is worth the peace of mind..


One thing that I always have to keep in mind is the way "facts" can be true but not paint the true picture. It is easy to slant this information to look like it matters. If you dig into the "facts" as reported, you often find they are used by people who have a financial interest. That makes it suspect and we need to look closer. One way to slant the truth is by doing the measurements under test conditions which don't match the way we use the tubing. 
One quick way to slant the results might be to test under really high pressure and a closed tube. If you put 100 PSI on a tube closed at the end, you will likely get far different results than if you use 30PSI and a diffuser at the end. 

I don't know how the tests were done and really don't care because I don't depend on ads to be truthful. On my tests of airline done under very simple conditions, like sticking the tubing under water, I see no loss of CO2. 
Just as a cross check, I asked a chemist at US Plastics for a recommendation. His company makes and sells many types of tubing and he could have recommended any of the common ones we use but his answer, after asking what conditions, was that it did not matter.


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## etk300ex (May 1, 2013)

I find it hard to believe there are very detailed reports on the subject lol, let alone more than one. I'd be interested to see if there are however. 

Even if, 20% of my co2 refill is $2. Air line $0.10/ft. CO2 proof $1/ft. I have two 25' lines. I'll risk it.


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## rdmustang1 (Oct 20, 2013)

PlantedRich said:


> One thing that I always have to keep in mind is the way "facts" can be true but not paint the true picture. It is easy to slant this information to look like it matters. If you dig into the "facts" as reported, you often find they are used by people who have a financial interest. That makes it suspect and we need to look closer. One way to slant the truth is by doing the measurements under test conditions which don't match the way we use the tubing.
> One quick way to slant the results might be to test under really high pressure and a closed tube. If you put 100 PSI on a tube closed at the end, you will likely get far different results than if you use 30PSI and a diffuser at the end.
> 
> I don't know how the tests were done and really don't care because I don't depend on ads to be truthful. On my tests of airline done under very simple conditions, like sticking the tubing under water, I see no loss of CO2.
> Just as a cross check, I asked a chemist at US Plastics for a recommendation. His company makes and sells many types of tubing and he could have recommended any of the common ones we use but his answer, after asking what conditions, was that it did not matter.


The thread was either on here or BR. I don't think the guy who did the math was in it for profit but he was referencing a website that manufactured tubing and used their permeation tables in his equations. Like I said, I'm not convinced but his math was sound and for the 3 feet of tubing I used it was either $1.49 for a package of 10' silicone tubing from the LFS or $1.50 for 3ft poly tubing from HD. To me it was a no brainer.


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## Mark Allred (May 3, 2013)

rdmustang1,
According to this chart from Cole Parmer, your polyurethane tubing is more permeable than vinyl tubing?
http://www.coleparmer.com/TechLibraryArticle/700


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## Subtletanks91 (May 29, 2013)

I'm just going to use regular airline tubing. For the small amount of co2 going into the tank and the short distance between the regulator check valve and diffuser no co2 will be lost anyways


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## rdmustang1 (Oct 20, 2013)

Mark Allred said:


> rdmustang1,
> According to this chart from Cole Parmer, your polyurethane tubing is more permeable than vinyl tubing?
> http://www.coleparmer.com/TechLibraryArticle/700


I'm using polyethylene which according to that chart is 28% less permeable than vinyl. 

However, I think my memory has played tricks on me again. Looking at that chart I think the 20% CO2 loss was based on using silicone tubing, not vinyl. Silicone is almost 100x as permeable compared to polyethylene. Apologies..


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## Darkblade48 (Jan 4, 2008)

Let's crunch some numbers.

Silicone has a permeability of 20,132 (cc-mmsec-cm2-cmHg) according to that table. Note that the units are as follows: 

*cc-mmsec-cm2-cmHg* - the flow of a gas in cubic centimeters per second per area in cm2 through a thickness in mm which has a pressure difference in cmHg

Also, that *the magnitude is to the -10 magnitude *(important!)

Typical OD of silicone tubing is 5 mm (3/16") with an ID of 4 mm, so a *wall thickness of 0.5 mm*.

Let's *assume the length of the tubing is 100 cm* (1 metre). We can calculate the surface area (top and bottom of the tubing's surface area (the ends) is essentially negligible in this calculation). Using the above length, we get a *surface area of 157.47 square cm*. 

*Typical pressure* is 30 PSI, or 206.84 kPa. Standard atmospheric pressure is 101.3 kPa, meaning the pressure difference is 105.54 kPa or 76.16 cmHg.

Let's assume this is over 1 second. 

So now, we have all the necessary values to substitute into the equation.

20,132 cubic centimetres of CO2 (to the -10th magnitude) is lost over a surface area of 1 square centimetres, with a wall thickness of 1 mm, over 1 second, with a pressure differential of 1 cmHg.

Thus, over 157.47 square cm, with a wall thickness of 0.5 mm, over 1 second, with a pressure differential of 76.16 cmHg works out to be:

120,720,684 cubic centimetres (to the -10th magnitude). This works out to be* 0.012 (rounded) cubic centimetres (mL) of gas per second. *

Now, to put this in real world terms. *A 10 pound cylinder of gas*, coming out at 30 PSI, at 25C *works out to be 1235.51L of gas* (10 pounds works out to be 103.09 moles).
*
Assuming you keep your CO2 on for 8 hours a day, you are losing 345.6 mL of gas a day, or about 0.028% of your gas per day (over 1 metre of tubing). *

Using similar calculations for vinyl tubing, you get a loss only 6.18 mL of gas per 8 hour day, over 1 metre of tubing. Tygon (for food/beverage, according to the Cole Pharmer site) yields slightly better results at 4.63 mL of gas per day, over 1 metre of tubing.

So, even in the worst case scenario with silicone, you are losing a negligible amount of CO2.

Hope this is useful for some


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## Mark Allred (May 3, 2013)

Thank you, Anthony! The math here was way over my head, but you put it into an understandable perspective! 
So vinyl (standard airline hose) loses a practically immeasurable percent of CO2 at 30 PSIG.
Those of us running reactors are probably seeing less than 1 PSIG, 
so the gas loss isn't even worth mentioning.
You should put this data on your "CO2 Primer"


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## rdmustang1 (Oct 20, 2013)

Based on your equation, if your tank lasts 6 months then you'll lose over 10% of your total CO2. That means over 180 days you lose 18 days worth of CO2. What's worse is take the guy who said he has a 25 foot run. Over 6 months he'd lose 83% of his CO2. That's not trivial to me. Of course like Mark said vinyl tubing should be fine. Just don't use silicone 

Here is a link to the previous example I had seen.

http://www.plantedtank.net/forums/showthread.php?p=213172#post213172


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## Darkblade48 (Jan 4, 2008)

Thanks for the kind words. It was a fun exercise for me as well. I have put it into my primer.

http://www.plantedtank.net/forums/showpost.php?p=1056450&postcount=8

Edit I just realized there is an error in my calculations. The amount of gas that is loss will be less. I calculated the wrong difference in pressure (155 cmHg is the difference between 30 PSI and a vacuum). I doubt anyone is running airline tubing in space 

I will fix the calculation shortly. The amount loss will be less.


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## Bettatail (Feb 12, 2009)

--losing 720 mL of gas a day, or about 0.058% of your gas per day (over 1 metre of tubing).--

Anthony, how many CC/mL of CO2 you pump into your planted tank per day? 

Don't use silicone air hose, regular vinyl is ok, industrial grade polyvinyl or PU, even better.


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## Darkblade48 (Jan 4, 2008)

Bettatail said:


> Anthony, how many CC/mL of CO2 you pump into your planted tank per day?
> 
> Don't use silicone air hose, regular vinyl is ok, industrial grade polyvinyl or PU, even better.


As I mentioned, there is a mistake above, and I will need to fix it (currently on my phone, so editing is a bit difficult). The actual amount loss is much smaller.

To put the issue of silicone tubing vs. vinyl tubing further into perspective, but when using silicone tubing (I assumed a "standard" length of 3 metres or 10 feet), you are looking at about 2 cents worth of CO2 being lost per 8 hour day (assuming 10 pounds of CO2 costs 20 dollars).

Edit: I have changed the information in the previous post above so that the information is now correct.



rdmustang1 said:


> Based on your equation, if your tank lasts 6 months then you'll lose over 10% of your total CO2. That means over 180 days you lose 18 days worth of CO2. What's worse is take the guy who said he has a 25 foot run. Over 6 months he'd lose 83% of his CO2. That's not trivial to me. Of course like Mark said vinyl tubing should be fine. Just don't use silicone


With the corrected information, if your tank lasts 6 months, then you'd lose about 5% of your total CO2. About 9 days of CO2. 

For a 25 foot run, over 6 months, that user would lose about significantly more (about 38% - with the corrected calculation). 

However, this being all said and done, this is all theoretical, and some of my math might be wrong, so I'll have to go over and think about this again.


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## Bettatail (Feb 12, 2009)

, still the same question...


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## Darkblade48 (Jan 4, 2008)

Bettatail said:


> Anthony, how many CC/mL of CO2 you pump into your planted tank per day?


I don't know. I haven't measured this before - is there some way to estimate this without a flow meter?

With some basic math, we can theoretically estimate.

4 mm ID tubing, means ~2 mm radius sphere. This makes a 33.5 mm^3 sphere

Assume 1 bubble per second, for 8 hours a day. 28800 bubbles, so 964,800 mm^3 or 964.8 mL a day.

So about 1L a day, at 1 bubble per second. This would translate to about 3 years at that rate...might sound about right (I was running about that rate on an ADA Mini-S for two years, and the cylinder still has liquid gas in it).


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## Bettatail (Feb 12, 2009)

I don't remember the math I did long time ago, but I think it is about 3-4CC/ML per minute, one bubble per second.

And 8 hours a day, one bubble per second, it is about 1500-2000 CC/ML, so the co2 lose using 2M silicone hose, it is some where between 25% to 50%....

add: search some of my old calculations about the flow volume, the actual daily injection is much lower than 1500-2000cc as stated above, and a 4mm bubble is more realistic.
2mm in diameter bubble, is 120cc daily injection one bubble per second.
4mm in diameter bubble, is 960cc daily injection one bubble per second.
http://www.plantedtank.net/forums/showpost.php?p=2811474&postcount=3


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## Bettatail (Feb 12, 2009)

Darkblade48 said:


> I don't know. I haven't measured this before - is there some way to estimate this without a flow meter?
> 
> With some basic math, we can theoretically estimate.
> 
> ...


from your daily co2 injection estimation, only 30% of co2 reach the water if over 2 meters silicone air hose.

so better not use silicone air hose for co2...


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## Subtletanks91 (May 29, 2013)

So since it's such a small tank I shouldn't be running a bunch of co2. But would making a spray to use in the spec and angling it downward toward the opposite bottom corner help keep the co2 bubbles down to dissolve them more and faster? Keeping the little co2 I use in the tank in theater compared to loosing it on the surface because it's only 4-6 inches away from the surface?


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## Darkblade48 (Jan 4, 2008)

Bettatail said:


> add: search some of my old calculations about the flow volume, the actual daily injection is much lower than 1500-2000cc as stated above, and a 4mm bubble is more realistic.
> 2mm in diameter bubble, is 120cc daily injection one bubble per second.
> 4mm in diameter bubble, is 960cc daily injection one bubble per second.
> http://www.plantedtank.net/forums/showpost.php?p=2811474&postcount=3


Okay, good, so our calculations for that match up. 



Bettatail said:


> from your daily co2 injection estimation, only 30% of co2 reach the water if over 2 meters silicone air hose.
> 
> so better not use silicone air hose for co2...


Again, I'm starting to suspect my own calculations. I find it a bit ridiculous that so much CO2 is lost if silicone tubing is used, since I have been using it for quite a long time (though I am only running about 1 metre of tubing, and not some longer lengths like 25 feet (almost 8 metres)). 

However, based on just the data in the table, one can see that silicone is about 56 times more permeable to CO2 than vinyl. 

What I want to know is how this was measured. I am also starting to suspect whether the pressure inside the tubing is actually 30 PSI (wouldn't we expect to see some swelling of the tube?). That leads to the final part of the problem - with an open end (e.g. a diffuser), does the pressure in the tubing build up to 30 PSI?



Subtletanks91 said:


> So since it's such a small tank I shouldn't be running a bunch of co2. But would making a spray to use in the spec and angling it downward toward the opposite bottom corner help keep the co2 bubbles down to dissolve them more and faster? Keeping the little co2 I use in the tank in theater compared to loosing it on the surface because it's only 4-6 inches away from the surface?


If you can keep the CO2 mist from reaching the surface by blowing them downwards, it will give them more time to dissolve into the water column, meaning less wasted CO2.


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## Subtletanks91 (May 29, 2013)

I have a crap load of tubing. And no idea how to tell if its fungal silicone or what. How do you tell


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## Darkblade48 (Jan 4, 2008)

Subtletanks91 said:


> I have a crap load of tubing. And no idea how to tell if its fungal silicone or what. How do you tell


Fungal silicone?

Silicone is very flexible. It typically is not clear (I usually see colours like blue and green).


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## Mark Allred (May 3, 2013)

Darkblade48 said:


> What I want to know is how this was measured. I am also starting to suspect whether the pressure inside the tubing is actually 30 PSI (wouldn't we expect to see some swelling of the tube?). That leads to the final part of the problem - with an open end (e.g. a diffuser), does the pressure in the tubing build up to 30 PSI?.


Good points! At 30 PSIG, I would be willing to bet you would have a silicone sausage (ever made a water weenie?)  I highly doubt you would see even close to 30 PSIG. Aren't a lot of these diffusers glass? They may not handle that sort of pressure.


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## rdmustang1 (Oct 20, 2013)

Mark Allred said:


> Good points! At 30 PSIG, I would be willing to bet you would have a silicone sausage (ever made a water weenie?)  I highly doubt you would see even close to 30 PSIG. Aren't a lot of these diffusers glass? They may not handle that sort of pressure.


This would be trivial to test. Reverse a check valve or tie a knot in the line. Then open your low end to 30 psi.


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## Darkblade48 (Jan 4, 2008)

rdmustang1 said:


> This would be trivial to test. Reverse a check valve or tie a knot in the line. Then open your low end to 30 psi.


Oh now this is interesting; you could probably test the permeability too!

Just inject the tubing with 30 PSI, then back off the regulator and see if the pressure drops (you'll have to ensure that the plugged end of the tubing is completely air tight).


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## rdmustang1 (Oct 20, 2013)

Darkblade48 said:


> Oh now this is interesting; you could probably test the permeability too!
> 
> Just inject the tubing with 30 PSI, then back off the regulator and see if the pressure drops (you'll have to ensure that the plugged end of the tubing is completely air tight).


Use a longer tubing to exacerbate the loss.


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## Bettatail (Feb 12, 2009)

Darkblade48 said:


> Oh now this is interesting; you could probably test the permeability too!
> 
> Just inject the tubing with 30 PSI, then back off the regulator and see if the pressure drops (you'll have to ensure that the plugged end of the tubing is completely air tight).


I have a digital mass flow meter, and I can test the flow rate that before and after a section of silicone air hose.
Don't have silicone air hose at the moment though.


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## PlantedRich (Jul 21, 2010)

So to me it gets back to simple things. 

Something like worry over how long it takes one ant to eat an elephant versus two ants? 

So if one is worried about the cost of feeding elephants to ants, maybe he should just stop buying elephants, stomp the ants and find a cheaper hobby? 

The difference in CO2 lost is not going to buy many elephants!


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## Darkblade48 (Jan 4, 2008)

PlantedRich said:


> So to me it gets back to simple things.
> 
> Something like worry over how long it takes one ant to eat an elephant versus two ants?
> 
> ...


Well, you're looking at about a loss of 2 cents a day, in terms of monetary value, when using silicone tubing.


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## rdmustang1 (Oct 20, 2013)

Darkblade48 said:


> Well, you're looking at about a loss of 2 cents a day, in terms of monetary value, when using silicone tubing.


CO2 is cheap. My time isn't. If spending $1 more for tubing gives me 2 more weeks of CO2 every refill then I have no problem upgrading my tubing.


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## jeremy va (Dec 22, 2012)

Ok, so:

1. If silicone loses 20% of the co2 that passes through it why don't we see bubbles coming out of the tube when we submerge it? I happen to drape my tubes through a holding tank all the time (and I use a variety of airlines/silicone etc.) The ONLY time I've seen a bubble is when I used a piece of tubing that was so old it was practically rotted. (I'm a tightwad).
2. If silicone loses 20% (or 30%) and produces no bubbles why has it not been adapted as a diffusion device? Basically a silicone membrane that is under enough pressure that it leaks the non-bubbles but not so much you have a balloon in the tank.

And no formulas please... -)


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## Bettatail (Feb 12, 2009)

If any of you have two identical inline bubble counter and a long section of silicone air hose, you can put the bubble counters on and before the silicone air hose, and use a super ceramic(atomizer) as diffuser( about 30 psi cracking, 25 psi running pressure), make sure the diffuser working correctly and placed at certain level in the water.

count the bubble rate from both bubble counter, do a simple math, and let us know the result, thanks.




jeremy va said:


> Ok, so:
> 
> 1. If silicone loses 20% of the co2 that passes through it why don't we see bubbles coming out of the tube when we submerge it? I happen to drape my tubes through a holding tank all the time (and I use a variety of airlines/silicone etc.) The ONLY time I've seen a bubble is when I used a piece of tubing that was so old it was practically rotted. (I'm a tightwad).
> 2. If silicone loses 20% (or 30%) and produces no bubbles why has it not been adapted as a diffusion device? Basically a silicone membrane that is under enough pressure that it leaks the non-bubbles but not so much you have a balloon in the tank.
> ...


you are so funny.


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## jeremy va (Dec 22, 2012)

I'm serious! Inquiring minds need to know!


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## PlantedRich (Jul 21, 2010)

I'm betting we all lose far more CO2 carelessly through leaving leaks that we lose through the sides of most tubing. The tubing is just such a small factor in CO2 loss when compared to what blows out the top of the tank that it is just not going to the top of my list. Better use of what I do get in the tank far outweights any concern with loss through the side of tubing.


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## Darkblade48 (Jan 4, 2008)

rdmustang1 said:


> CO2 is cheap. My time isn't. If spending $1 more for tubing gives me 2 more weeks of CO2 every refill then I have no problem upgrading my tubing.


Agreed. Fact is, vinyl tubing is usually cheaper than silicone tubing too 



jeremy va said:


> Ok, so:
> 
> 1. If silicone loses 20% of the co2 that passes through it why don't we see bubbles coming out of the tube when we submerge it?


Water exerts more pressure than atmospheric air. This will change permeation rate, as per the formula mentioned previously.



jeremy va said:


> 2. If silicone loses 20% (or 30%) and produces no bubbles why has it not been adapted as a diffusion device? Basically a silicone membrane that is under enough pressure that it leaks the non-bubbles but not so much you have a balloon in the tank.


As I mentioned, my calculations might be wrong; when I have more time, I will go and review them again.

As I also mentioned, the fact of the matter is that silicone tubing is significantly more permeable to CO2 than vinyl tubing, but in the "real world," it might not actually be that much.



PlantedRich said:


> I'm betting we all lose far more CO2 carelessly through leaving leaks that we lose through the sides of most tubing. The tubing is just such a small factor in CO2 loss when compared to what blows out the top of the tank that it is just not going to the top of my list. Better use of what I do get in the tank far outweights any concern with loss through the side of tubing.


I agree. The actual loss of CO2 is probably much lower than I estimated. I still am not sure how they measured those values, so cannot be certain whether my calculations are correct.


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## rdmustang1 (Oct 20, 2013)

PlantedRich said:


> I'm betting we all lose far more CO2 carelessly through leaving leaks that we lose through the sides of most tubing. The tubing is just such a small factor in CO2 loss when compared to what blows out the top of the tank that it is just not going to the top of my list. Better use of what I do get in the tank far outweights any concern with loss through the side of tubing.


That's like saying "My house is on fire and the car is in the garage. I've already lost so much money from the burning house I'm not going to bother saving my car."

Again, if there is even a chance that I can get 2 more weeks of CO2 every refill I'll replace my tubing with a cheap alternative. Maybe your time is even more valuable than mine and the time it takes to find better tubing isn't worth it to you. That's fine. I'm not so lucky.


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## jeremy va (Dec 22, 2012)

Anthony,

I'm not asking this question to "call you out" on your math and I was teasing on the formulas -- I hope it didn't come across as being snotty. I'm genuinely baffled by this topic because I have read repeatedly on this board and elsewhere and been told by other aquarists that "non-co2" tube leaks co2 (some use figures like 20%) unless it is the "approved" type. This is also referenced by companies that sell tubing -- GLA, for example, sells "CO2 resistant tubing" and says: "This is NOT silicone tubing which is highly permeable to CO2. With our CO2 resistant tubing, CO2 will not escape and every last drop of CO2 will be put to efficient use." 

This has never made sense to me because if any significant amount -- even 5% of throughput -- is lost, then I would think one would see a mist or bubbles if a goodly length of tube is submerged in water. Maybe this is as someone said -- a case of internet parrotry or perhaps "permeability" (which could be a loss of .00001%) has been inflated by tubing salesman to the point where otherwise sensible people fear leaks and buy only "approved" tubing. 

My guess (based only on the fact that I don't see bubbles or mist) is that any loss is so low as to be insignificant -- let's say in the region of 1%. I think if it were even 5% we would see bubbles when the tube is submerged in water.


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## Darkblade48 (Jan 4, 2008)

jeremy va said:


> This has never made sense to me because if any significant amount -- even 5% of throughput -- is lost, then I would think one would see a mist or bubbles if a goodly length of tube is submerged in water.


As I mentioned, when you submerge the tubing into water, I suspect that the pressure differential will change slightly. Whether this will be enough to prevent the gas from escaping, I do not know.



jeremy va said:


> Maybe this is as someone said -- a case of internet parrotry or perhaps "permeability" (which could be a loss of .00001%) has been inflated by tubing salesman to the point where otherwise sensible people fear leaks and buy only "approved" tubing.


Yes, this is also very probable. I have used silicone tubing, and it has worked for me. It is what I had at hand, but maybe in the future, if I see some vinyl tubing on sale (and remember to buy it), then I will pick some up.

I do not see the point of paying the premium, however, for "CO2 resistant" tubing.



jeremy va said:


> My guess (based only on the fact that I don't see bubbles or mist) is that any loss is so low as to be insignificant -- let's say in the region of 1%. I think if it were even 5% we would see bubbles when the tube is submerged in water.


It is possible. All of my math is purely speculative, and theoretical calculations (can and often) vary from actual experimental data.


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## jeremy va (Dec 22, 2012)

Anthony said: "As I mentioned, when you submerge the tubing into water, I suspect that the pressure differential will change slightly. Whether this will be enough to prevent the gas from escaping, I do not know."

Ahhhhh....now I get it! Water is denser and heavier than air so it could sorta "hold the co2 in" and prevent the loss (if there is any loss). 

Nothing is ever simple...


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## etk300ex (May 1, 2013)

Good chat! 

Nice work Darkblade, felt like I was back sitting in fluid dynamics class for a second haha.

I have 50' total of vinyl tubing, 5lb tank, been running for about 6 months now, we'll just have to see how long it lasts... I fortunately have a drive thru beer store 5 minutes away, dont even have to get out of my truck to exchange


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## Darkblade48 (Jan 4, 2008)

jeremy va said:


> Ahhhhh....now I get it! Water is denser and heavier than air so it could sorta "hold the co2 in" and prevent the loss (if there is any loss).
> 
> Nothing is ever simple...


It's not really doing that...water exerts pressure, so it might be enough to mitigate CO2 permeability out of the tubing.

Think what happens when you put a plastic bag around your hand and submerge it into water. The bag clings to your hand (this is water pressure at play).


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## jeremy va (Dec 22, 2012)

OK, great. Bottom line: use airline tubing, your co2 mileage may vary but only by a little teeny bit. Probably. (;-)


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## Bettatail (Feb 12, 2009)

just don't use silicone air hose for co2, gentlemen.

BTW, lab/industrial grade low permeability silicone air hose, is ok.

base on the calculation of co2 permeability, co2 lost is about 20% using regular silicone air hose, at 0-5 psi. and from the Darkblade48's calculation above, you can see the lost is as high as 70% if the pressure is 30 psi, assume daily injection is 1000mL/CC of co2 over 2 meters of silicone.
(Not sure Darkblade48's calculation is 100% perfect, because I remember long time ago when I made the calculation, the percentage of co2 lose is about 20% but don't remember the length of the silicone air hose or the pressure, someone need to dig out the old thread)

One bubble per second, 2 meters silicone air hose, the co2 escape without passing through diffuser, is 20%-70%.

5lb co2 tank, $20 refill, using silicone air hose means $4-$14 wasted each refill, and the time between refill is shorten, more work.


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## jeremy va (Dec 22, 2012)

Bettatail,

So do you agree with Anthony that the reason we don't see bubbles if silicone tubing (carrying co2 at 30psi) is submerged is because the water pressure "mitigates" the permeability?


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## Bettatail (Feb 12, 2009)

jeremy va said:


> Bettatail,
> 
> So do you agree with Anthony that the reason we don't see bubbles if silicone tubing (carrying co2 at 30psi) is submerged is because the water pressure "mitigates" the permeability?


can you see the bacteria?

why do I have to see the bubbles if co2 escape through the silicone air hose if it is submerged?


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## jeremy va (Dec 22, 2012)

Good point. My thinking was that I can sure as heck see them when they come out of the diffuser so, if I'm losing them at the rate of 20%-70% I should be able to see SOMETHING coming out of the silicone (when under water). I suppose they could be so tiny that they are like bacteria and invisible. If I had two bubble counters I'd try the test you mentioned. Maybe there is another way I can figure out


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## rdmustang1 (Oct 20, 2013)

jeremy va said:


> Good point. My thinking was that I can sure as heck see them when they come out of the diffuser so, if I'm losing them at the rate of 20%-70% I should be able to see SOMETHING coming out of the silicone (when under water). I suppose they could be so tiny that they are like bacteria and invisible. If I had two bubble counters I'd try the test you mentioned. Maybe there is another way I can figure out


Surface area of a diffuser is much less than surface area of a 25' silicone tube. To permiate the tubing the bubbles would be extremely small and spread out.


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## oldpunk78 (Nov 1, 2008)

You guys are barking up the wrong tree. The biggest difference between the vinyl, silicone, and urethane types is that the first two are more susceptible to chemically reacting with the tubing ccausing it to become hard and brittle over time. This happens a lot faster is the tubing is exposed to water like at reactor connection or where the tubing meats a diffuser under water. Gas loss is negligible.


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## rdmustang1 (Oct 20, 2013)

oldpunk78 said:


> You guys are barking up the wrong tree. The biggest difference between the vinyl, silicone, and urethane types is that the first two are more susceptible to chemically reacting with the tubing ccausing it to become hard and brittle over time. This happens a lot faster is the tubing is exposed to water like at reactor connection or where the tubing meats a diffuser under water. Gas loss is negligible.


A few people have commented that their vinyl and silicone tubing has lasted for years without getting brittle. I have no experience but rather just repeating what was said recently. Maybe it varies based on manufacturer?

The math shows that the gas loss is not negligible. Whether that translates into real life is unknown.


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## Darkblade48 (Jan 4, 2008)

Bettatail said:


> BTW, lab/industrial grade low permeability silicone air hose, is ok.


Need data for this before making conclusions.



Bettatail said:


> and from the Darkblade48's calculation above, you can see the lost is as high as 70% if the pressure is 30 psi, assume daily injection is 1000mL/CC of co2 over 2 meters of silicone.


I believe i mentioned it was 3 metres in my calculation. 




Bettatail said:


> One bubble per second, *2 meters* silicone air hose, the co2 escape without passing through diffuser, is 20%-70%.


3 metres 

Again, I'm not sure if the calculations are correct, as I did them quickly over a break at work.

Regardless to say, silicone tubing should not be used. If it is used, keep the lengths short to avoid lots of wasted gas.



oldpunk78 said:


> You guys are barking up the wrong tree. The biggest difference between the vinyl, silicone, and urethane types is that the first two are more susceptible to chemically reacting with the tubing ccausing it to become hard and brittle over time. This happens a lot faster is the tubing is exposed to water like at reactor connection or where the tubing meats a diffuser under water. Gas loss is negligible.





rdmustang1 said:


> A few people have commented that their vinyl and silicone tubing has lasted for years without getting brittle. I have no experience but rather just repeating what was said recently. Maybe it varies based on manufacturer?
> 
> The math shows that the gas loss is not negligible. Whether that translates into real life is unknown.


Definitely, carbonic acid can affect different materials in different manners. New vs. old silicone tubing (or vinyl, or urethane, etc) might have different permeability. 

Also...please don't take my calculations blindly and verify yourself 

Edit: *Uh oh. I might have made a mistake* (looking over my calculations again). As a material thickness increases, you would expect to get less gas loss, right? That is to say, gas permeability is inversely related to gas flow (loss)?


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## jeremy va (Dec 22, 2012)

One reason I'm interested in this topic is because the seven tanks that I have that need co2 are obtaining it through an embarrassing patchwork of bits and pieces -- some bits are probably at least 10 years old.

So I started looking at tubing (I'm using Swagelok fittings pretty much everywhere) and none of it is very helpful -- in fact, some of the aquatic vendors make things a bit more confusing:

Swagelok, offers a 1/8"ID/1/4"OD (0.125" ID) vinyl tube in 100' rolls that is .63 cents a foot. (LT-2-4). Obviously, Swagelok is a name to trust but they don't say it is rated for gas. And their web site confusingly mixes metric and inched and lists the Tube fitting into which the tube fits as "6 mm Tube OD x 1/8 in" which implies that you need tube that is 6mm wide x 1/8". 6mm is actually .236" so I have to assume it would work with their 1/4" fittings...

Lowes offers 0.170" ID/ 1/4" PVC tube at .15 cents a foot. My kind of price but at .170 not sure if it would work...

ADANA offers 6' lengths of "pressure proof" tube at just over $1/foot but doesn't bother to include the size/material etc. (Since their site is written in pidgin-english the specs would probably be unintelligible anyway).

Marine depot offers "CO2 proof" tube in 4mmID/6mmOD blue, black or green (unacceptable). Priced at $1 foot.

GLA offers 4mm/6mm clear at $1/foot and a number people on TPT use it. They jutss say it isn't silicone.

Anybody have a recommendation?


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## Darkblade48 (Jan 4, 2008)

Get the cheapest vinyl tubing you can at the hardware store. As long as it fits, it will work.

Save yourself the headache of looking for the "best" stuff, unless you intend to pay a premium for it.

Edit: Also meant to add that it's really not worth worrying about whether one type of tubing (say vinyl) is slightly worse than a "premium CO2 resistant" tubing or not. As long as it's not silicone, you'll be fine (that being said, silicone is _probably_ going to be OK, but I still need to rework the actual amount of gas that is lost when compared to vinyl tubing).


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## Mark Allred (May 3, 2013)

Darkblade48 said:


> Get the cheapest vinyl tubing you can at the hardware store. As long as it fits, it will work.
> 
> Save yourself the headache of looking for the "best" stuff, unless you intend to pay a premium for it.


+One


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## rdmustang1 (Oct 20, 2013)

Personally I went with polyethylene because it came in black


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## Bettatail (Feb 12, 2009)

Darkblade48 said:


> Need data for this before making conclusions.
> 
> 
> I believe i mentioned it was 3 metres in my calculation.
> ...


the lab grade silicone has additive to prevent gas lost, there are PDF and spec sheet that clearly list the co2 permeability for most of the lab/industrial grade name brand silicone air hose, you need to find them.

the 70% lost over 2 meters is base on your calculation.
from your calculation, co2 lost over 1 meter regular silicone air hose, is 342ml, am I correct? so 2 meters of air hose, lost is about 700ml. 
700ml over 1000ml daily injection(only 300ml inject into fish tank), is 70% lost.

BTW, there is no point cling to the numbers anymore, we now know regular silicone air hose has high permeability, there is significant amount of co2 lost and better not use regular silicone air hose for co2.



Darkblade48 said:


> Get the cheapest vinyl tubing you can at the hardware store. As long as it fits, it will work.
> 
> Save yourself the headache of looking for the "best" stuff, unless you intend to pay a premium for it.
> 
> Edit: Also meant to add that it's really not worth worrying about whether one type of tubing (say vinyl) is slightly worse than a "premium CO2 resistant" tubing or not. As long as it's not silicone, you'll be fine (that being said, silicone is _probably_ going to be OK, but I still need to rework the actual amount of gas that is lost when compared to vinyl tubing).


Anthony, please, you are using silicone or regular hose, others may prefer something better, it is not "premium" cost anyway because $1/ft for 7 ft, it is only $7, the industrial/lab grade may last over 10 years.
It is fine if you want to save more and "go cheap", but before you do that you need to understand the real difference between and items you pick, and the opportunity cost.

regular vinyl is ok, but 2-3 year, require replacement because the UV damage, industrial grade air hose is much better than the regular vinyl, 10+ years before replacement.
and I think me and others had enough talk about the pro and con to pick between regular air hose or the industrial/lab grade for co2, simply *search the forum*, you will see a lot of information.


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## jeremy va (Dec 22, 2012)

So Bettatail, where do you buy industrial grade that will work with a standard Swagelok tube/ferrule/nut compression fitting ( the B-400 series). Is the Swagelok hose (LT-2-4) "industrial grade" or do you have to troll ebay or what?


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## Bettatail (Feb 12, 2009)

jeremy va said:


> So Bettatail, where do you buy industrial grade that will work with a standard Swagelok tube/ferrule/nut compression fitting ( the B-400 series). Is the Swagelok hose (LT-2-4) "industrial grade" or do you have to troll ebay or what?


clippard offer direct sale, the polyurethane lab grade air hose.

and USplastic, offer more types from different manufactures, lab/industrial grade, you need to do a research on which type you need first, or you will get lost, too many to choose from.

bulk order can be as low as $0.10/ft, my friend.


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## jeremy va (Dec 22, 2012)

OK, I appreciate it. I always get lost on those kinds of sites anyway so it's good to have a warning (;-)


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## Mark Allred (May 3, 2013)

rdmustang1 said:


> Personally I went with polyethylene because it came in black


Once you go black, you never come back.


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## Darkblade48 (Jan 4, 2008)

Bettatail said:


> the 70% lost over 2 meters is base on your calculation.
> from your calculation, co2 lost over 1 meter regular silicone air hose, is 342ml, am I correct? so 2 meters of air hose, lost is about 700ml.
> 700ml over 1000ml daily injection(only 300ml inject into fish tank), is 70% lost.


This is why I think my calculation is wrong. 

If you are only injecting 1000 mL a day, but you had (say) 5 metres of tubing, then you would lose 1500 mL of gas a day, which is more than the injected amount.

The 1000 mL of gas a day is assuming that you are looking at a bubble counter that is immediately after the needle valve, correct?



Bettatail said:


> BTW, there is no point cling to the numbers anymore, we now know regular silicone air hose has high permeability, there is significant amount of co2 lost and better not use regular silicone air hose for co2.


Correct.



Bettatail said:


> Anthony, please, you are using silicone or regular hose, others may prefer something better, it is not "premium" cost anyway because $1/ft for 7 ft, it is only $7, the industrial/lab grade may last over 10 years.


I only recommend regular hose because it is cheap(er) than specialty tubing. However, users are free to choose whatever they want. Sometimes it is easier to just stop off at the hardware store and pick up some cheap tubing rather than hunting for Tygon 



Bettatail said:


> and I think me and others had enough talk about the pro and con to pick between regular air hose or the industrial/lab grade for co2, simply *search the forum*, you will see a lot of information.


Agreed. Ultimately, the end user makes the choice.


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## Bettatail (Feb 12, 2009)

Anthony, your calculation is alright, it is just all conditions to get the result, are static.

5 meters of silicone air hose, with daily 1000ml passing through bubble counter, there is possibility that you may not see any bubble come out of the atomizer type diffuser, because co2 escape from the air hose is more than the co2 passing through the bubble counter and fail to sustain the pressure at or above the point to push through diffuser.
escaping and injecting(passing through bubble counter) will come to an equilibrium point at certain pressure point, still lower than the cracking pressure to push through the diffuser.

it is a talk on paper though, someone need to get his hands wet to see the real deal.
(I believe I had a case before, one of the hobbyists bought a system from me, use his own air hose, he set it less than a bubble per second injection but didn't see anything came out from the diffuser. It was a real headache to guide him through the process to check any possible leaks, couldn't find any. finally the system sent back to me, tested twice, just nothing wrong with it, then sent back to the guy, with co2 hose, diffuser this time, problem no more)


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