What is leak proof co2 tubing made out of? Is polyethylene tubing co2 leak proof? I would like to get some in town at all possible as Idon't want to order just one item and pay shipping. Thanks for any help.
co2 tubing ?
- Thread starter tinkerman
- Start date
Tinkerman,
Cole-Parmer Technical Library
You might have already seen this link, but it is the table that most people refer to when comparing the permeability of CO2 through the different types of tubing. The "permeability of CO2" rating is the fourth column from the right.
I think the biggest point to notice is the fact that silicone aquarium tubing leaks 40x+ more CO2 into the surrounding air than pretty much any other type of commonly used tubing does, so silicone tubing would not be a good choice. Other than that, what I have heard is that the main benefit of the stuff that is sold as "CO2 tubing" is that it doesn't get firm or brittle nearly as quickly as the regular vinyl airline tubing does, so it doesn't need replacement as often.
Have a good one, Jeremy
Cole-Parmer Technical Library
You might have already seen this link, but it is the table that most people refer to when comparing the permeability of CO2 through the different types of tubing. The "permeability of CO2" rating is the fourth column from the right.
I think the biggest point to notice is the fact that silicone aquarium tubing leaks 40x+ more CO2 into the surrounding air than pretty much any other type of commonly used tubing does, so silicone tubing would not be a good choice. Other than that, what I have heard is that the main benefit of the stuff that is sold as "CO2 tubing" is that it doesn't get firm or brittle nearly as quickly as the regular vinyl airline tubing does, so it doesn't need replacement as often.
Have a good one, Jeremy
Tinkerman,
Cole-Parmer Technical Library
You might have already seen this link, but it is the table that most people refer to when comparing the permeability of CO2 through the different common types of tubing. The "permeability of CO2" rating is the fourth column from the right.
I think the biggest point to notice from the table is that silicone aquarium tubing leaks 40x+ more CO2 into the surrounding air than pretty much any other type of commonly used tubing does, so silicone tubing would be the worst choice by a large margin.
Have a good one, Jeremy
Cole-Parmer Technical Library
You might have already seen this link, but it is the table that most people refer to when comparing the permeability of CO2 through the different common types of tubing. The "permeability of CO2" rating is the fourth column from the right.
I think the biggest point to notice from the table is that silicone aquarium tubing leaks 40x+ more CO2 into the surrounding air than pretty much any other type of commonly used tubing does, so silicone tubing would be the worst choice by a large margin.
Have a good one, Jeremy
jeremy v Thanks for the link is good to know about how much the silacon tubing leaks that I am using at the moment.
Those gas permeability tables show up many times, in an argument about how bad silicone tubing is with CO2. I just worked my way through the meaning of permeability in that context and came up with a number for how many bubbles per second of CO2 you would lose using silicone tubing between the needle valve and the aquarium. The number I get is somewhere around a thousandth of a bubble per second, at a CO2 flow rate of one bubble per second. I don't claim this is accurate, but I do think it is about the right order of magnitude.
Try submerging a piece of silicone tubing with CO2 flowing through it in the water. You won't see CO2 bubbles forming on the tubing. People who use silicone tubing don't find that they can't get CO2 up to the tank. One reason for all of this is that the pressure of the CO2 inside the tubing is almost exactly the same as that of the air on the outside of the tubing. At worst, the partial pressure of the CO2 inside is 15 psi vs 0 on the outside. That is not much pressure for forcing a gas to pass through a thick piece of any kind of rubber.
The permeability number for silicone looks awesome until you notice that it is to be multiplied by ten to the minus tenth power. So, 20,000 times ten to the minus tenth is .000002. That is a tiny number.
The loss of CO2 through the tubing walls is proportional to the area of the walls in contact with the CO2. But our tubing is about 1/8 inch in inside diameter, or .3 cm. A one meter length of the tubing would only have an area of 100 square cm, not a big area. So, the combination of very low pressure inside the tubing, with a small area of tubing exposed to the CO2, and the very small permeability, leaves you with a tiny loss of CO2.
I hope one of my fellow engineers here will take more time than I did to work this out, and see how wrong I am.
Try submerging a piece of silicone tubing with CO2 flowing through it in the water. You won't see CO2 bubbles forming on the tubing. People who use silicone tubing don't find that they can't get CO2 up to the tank. One reason for all of this is that the pressure of the CO2 inside the tubing is almost exactly the same as that of the air on the outside of the tubing. At worst, the partial pressure of the CO2 inside is 15 psi vs 0 on the outside. That is not much pressure for forcing a gas to pass through a thick piece of any kind of rubber.
The permeability number for silicone looks awesome until you notice that it is to be multiplied by ten to the minus tenth power. So, 20,000 times ten to the minus tenth is .000002. That is a tiny number.
The loss of CO2 through the tubing walls is proportional to the area of the walls in contact with the CO2. But our tubing is about 1/8 inch in inside diameter, or .3 cm. A one meter length of the tubing would only have an area of 100 square cm, not a big area. So, the combination of very low pressure inside the tubing, with a small area of tubing exposed to the CO2, and the very small permeability, leaves you with a tiny loss of CO2.
I hope one of my fellow engineers here will take more time than I did to work this out, and see how wrong I am.
Vaughn,
I posted that link to the table, because I already had the link book marked on my browser. I originally saved the link because I was looking into designing a CO2 distribution manifold for feeding multiple tanks and I wanted to see what my diffusive losses would be if I ended up using around 15’ of ½” SCH40 PVC.
I used the PVC value from the table I linked to, 0.06cc for my bubble size, the exact actual ID and OD of SCH40 ½” PVC, 10psi as my line pressure, 20bubbles/sec as my flow rate, the pipe outside diameter for calculating the total surface area, etc. With that bubble rate of CO2 flowing for 24 hours a day I came up with a loss of 0.009% of my total CO2. I breathe out more CO2 than that with every breath I take, so needless to say I was happy with that result, and I will be using PVC for my future distribution manifold.
I never did the calcs for tubing since my tubing is always running at 1psi or less I never thought it would make a difference one way or the other. That’s why I just use regular vinyl airline for my setup, instead of anything “CO2 proof”. I just kept the lengths of airline short just in case I realized later that I was wrong in my assumption and it did in fact leak a noticeable percentage of CO2, haha.
You caught me though Vaughn, you reeled me in with your post. I felt compelled to take your challenge and try the calcs again, only for the tubing losses this time. I only did two calcs though. I figured what would possibly be the worst-case scenario for any planted tank setup. I calculated for a 10’ long tubing run, silicone tubing, 5 bubbles per second flow rate, 0.06cc bubble size, and 10psi pressure within the silicone tube. The only area (that I know of as of now) I might be in error with my calcs was in calculating the surface area of the tubing. I didn’t know whether the tubing inside surface area was what mattered, outside surface area, or possibly the average of the two. I used the average of the two. I also couldn’t find a specific ID and OD for silicone tubing, so I used the values of 3/16” ID and ¼” OD (which is the ID and OD for regular vinyl airline) instead.
I found that with the aforementioned specs I ended up with a CO2 loss of 0.54%. That was with the worst possible tubing material of them all by far in as far as permeability (silicone), 10’ length, 5 bubble per second flow rate, and 10psi of pressure in the tubing.
I then realized that the losses might actually be worse with lower flow rates, so I recalculated it for a 1 bubble per second flow rate instead. I ended up with a loss calculation of 0.81% of total CO2.
Those situations both greatly exceed the conditions that 99% of us are using the tubing for, so in my opinion I agree with you Vaughn, there is no real benefit to using special “CO2 proof” tubing.
I guess this CO2 leakage thing is really possibly just a rumor that was started by the people that make the “good” stuff in order to sell more expensive tubing.
I would be a little careful about using something like that as proof of your calculations though. CO2 could be leaking through the tubing quite fast and still just be dissolving directly into the water without ever first forming bubbles on the sides of the tubing (i.e. permeable membrane technology). You can also leak a lot of CO2 through the tubing and still have the exact same pressure at the end of the line. The CO2 pressure regulator will try its’ best to ensure the pressure in the line will remain constant no matter what the flow rate is, so (with leaking through the tubing) the flow rate out of the CO2 regulator would increase in order to keep the output pressure constant, and that is all that would change. It would work like a soaker hose for the yard. That type of hose leaks a lot of water through little pinholes along its’ length, but you can still easily hook up a spray nozzle to the far end and use it just like a normal hose if you wanted to without noticing any real difference in flow through the spray nozzle.
Have a good one, Jeremy
P.S.- I heard that you can lose up to 20% of your dissolved CO2 in an acrylic aquarium through the acrylic itself, so everyone should use glass tanks if they want to successfully grow plants. It was a very interesting tidbit of information that my local glass aquarium manufacturer told me. I have troubles growing plants sometimes, so I think I am going to go out and buy a glass aquarium to replace my acrylic one and see if that helps. Ouch, I think I just bit my tongue. I guess I shouldn’t stick it so far into my cheek and then bite down on it, haha.
P.S.S.- I just wanted to add that I am in no way making fun of the original starter of this thread. It was a great question and I am really glad the question was asked, because I was able to learn something that I wasn’t totally sure about before now, and I am always grateful to anyone that can help me to grow in wisdom. Hopefully this helps someone else too. Maybe now some other people that really enjoy this hobby and who might be short on money can save a little bit of what they do have by not bothering with buying (or wondering if they need) the more expensive tubing for their CO2 systems.
P.S.S.- If anyone sees that my calcs are off, to the point that the conclusion that Vaughn and I have now both drawn might be wrong, let me know. I don't want to be spreading false info just because I accidentally made a mistake in my math.
I posted that link to the table, because I already had the link book marked on my browser. I originally saved the link because I was looking into designing a CO2 distribution manifold for feeding multiple tanks and I wanted to see what my diffusive losses would be if I ended up using around 15’ of ½” SCH40 PVC.
I used the PVC value from the table I linked to, 0.06cc for my bubble size, the exact actual ID and OD of SCH40 ½” PVC, 10psi as my line pressure, 20bubbles/sec as my flow rate, the pipe outside diameter for calculating the total surface area, etc. With that bubble rate of CO2 flowing for 24 hours a day I came up with a loss of 0.009% of my total CO2. I breathe out more CO2 than that with every breath I take, so needless to say I was happy with that result, and I will be using PVC for my future distribution manifold.
I never did the calcs for tubing since my tubing is always running at 1psi or less I never thought it would make a difference one way or the other. That’s why I just use regular vinyl airline for my setup, instead of anything “CO2 proof”. I just kept the lengths of airline short just in case I realized later that I was wrong in my assumption and it did in fact leak a noticeable percentage of CO2, haha.
You caught me though Vaughn, you reeled me in with your post. I felt compelled to take your challenge and try the calcs again, only for the tubing losses this time. I only did two calcs though. I figured what would possibly be the worst-case scenario for any planted tank setup. I calculated for a 10’ long tubing run, silicone tubing, 5 bubbles per second flow rate, 0.06cc bubble size, and 10psi pressure within the silicone tube. The only area (that I know of as of now) I might be in error with my calcs was in calculating the surface area of the tubing. I didn’t know whether the tubing inside surface area was what mattered, outside surface area, or possibly the average of the two. I used the average of the two. I also couldn’t find a specific ID and OD for silicone tubing, so I used the values of 3/16” ID and ¼” OD (which is the ID and OD for regular vinyl airline) instead.
I found that with the aforementioned specs I ended up with a CO2 loss of 0.54%. That was with the worst possible tubing material of them all by far in as far as permeability (silicone), 10’ length, 5 bubble per second flow rate, and 10psi of pressure in the tubing.
I then realized that the losses might actually be worse with lower flow rates, so I recalculated it for a 1 bubble per second flow rate instead. I ended up with a loss calculation of 0.81% of total CO2.
Those situations both greatly exceed the conditions that 99% of us are using the tubing for, so in my opinion I agree with you Vaughn, there is no real benefit to using special “CO2 proof” tubing.
I guess this CO2 leakage thing is really possibly just a rumor that was started by the people that make the “good” stuff in order to sell more expensive tubing.
I would be a little careful about using something like that as proof of your calculations though. CO2 could be leaking through the tubing quite fast and still just be dissolving directly into the water without ever first forming bubbles on the sides of the tubing (i.e. permeable membrane technology). You can also leak a lot of CO2 through the tubing and still have the exact same pressure at the end of the line. The CO2 pressure regulator will try its’ best to ensure the pressure in the line will remain constant no matter what the flow rate is, so (with leaking through the tubing) the flow rate out of the CO2 regulator would increase in order to keep the output pressure constant, and that is all that would change. It would work like a soaker hose for the yard. That type of hose leaks a lot of water through little pinholes along its’ length, but you can still easily hook up a spray nozzle to the far end and use it just like a normal hose if you wanted to without noticing any real difference in flow through the spray nozzle.
Have a good one, Jeremy
P.S.- I heard that you can lose up to 20% of your dissolved CO2 in an acrylic aquarium through the acrylic itself, so everyone should use glass tanks if they want to successfully grow plants. It was a very interesting tidbit of information that my local glass aquarium manufacturer told me. I have troubles growing plants sometimes, so I think I am going to go out and buy a glass aquarium to replace my acrylic one and see if that helps. Ouch, I think I just bit my tongue. I guess I shouldn’t stick it so far into my cheek and then bite down on it, haha.
P.S.S.- I just wanted to add that I am in no way making fun of the original starter of this thread. It was a great question and I am really glad the question was asked, because I was able to learn something that I wasn’t totally sure about before now, and I am always grateful to anyone that can help me to grow in wisdom. Hopefully this helps someone else too. Maybe now some other people that really enjoy this hobby and who might be short on money can save a little bit of what they do have by not bothering with buying (or wondering if they need) the more expensive tubing for their CO2 systems.
P.S.S.- If anyone sees that my calcs are off, to the point that the conclusion that Vaughn and I have now both drawn might be wrong, let me know. I don't want to be spreading false info just because I accidentally made a mistake in my math.
Vaughn,
I just posted that link to the table, because I already had the link bookmarked on my browser. I originally saved the link because I was looking into designing a CO2 distribution manifold for feeding multiple tanks and I wanted to see what my diffusive losses would be if I ended up using around 15’ of ½” SCH40 PVC.
I used the PVC value from the table I linked to, 0.06cc for my bubble size, the exact actual ID and OD of SCH40 ½” PVC, 10psi as my line pressure, 20bubbles/sec as my flow rate, the pipe outside diameter for calculating the total surface area, etc. With that bubble rate of CO2 flowing for 24 hours a day I came up with a loss of 0.009% of my total CO2. I breathe out more CO2 than that with every breath I take, so needless to say I was happy with that result, and I will be using PVC for my future distribution manifold.
I never did the calcs for tubing since my tubing is always running at 1psi or less I never thought it would make a difference one way or the other. That’s why I just use regular vinyl airline for my setup, instead of anything “CO2 proof”. I just kept the lengths of airline short just in case I realized later that I was wrong in my assumption and it did in fact leak a noticeable percentage of CO2, haha.
You caught me though Vaughn, you reeled me in with your post. I felt compelled to take your challenge and try the calcs again, only for the tubing losses this time. I only did two calcs though. I figured what would possibly be the worst-case scenario for any planted tank setup. I calculated for a 10’ long tubing run, silicone tubing, 5 bubbles per second flow rate, 0.06cc bubble size, and 10psi pressure within the silicone tube. The only area (that I know of as of now) I might be in error with my calcs was in calculating the surface area of the tubing. I didn’t know whether the tubing inside surface area was what mattered, outside surface area, or possibly the average of the two. I used the average of the two. I also couldn’t find a specific ID and OD for silicone tubing, so I used the values of 3/16” ID and ¼” OD (which is the ID and OD for regular vinyl airline) instead.
I found that with the aforementioned specs I ended up with a CO2 loss of 0.54%. That was with the worst possible tubing material of them all by far in as far as permeability (silicone), 10’ length, 5 bubble per second flow rate, and 10psi of pressure in the tubing.
I then realized that the losses might actually be worse with lower flow rates, so I recalculated it for a 1 bubble per second flow rate instead. I ended up with a loss calculation of 0.81% of total CO2.
Those situations both greatly exceed the conditions that 99% of us are using the tubing for, so in my opinion I agree with you Vaughn, there is no real benefit to using special “CO2 proof” tubing.
I guess this CO2 leakage thing is really possibly just a rumor that was started by the people that make the “good” stuff in order to sell more expensive tubing.
I would be a little careful about using something like that as proof of your calculations though. CO2 could be leaking through the tubing quite fast and still just be dissolving directly into the water without ever first forming bubbles on the sides of the tubing (i.e. semipermeable membrane technology for diffusing CO2 directly into water). You can also leak a lot of CO2 through the tubing and still have the exact same pressure at the end of the line. The CO2 pressure regulator will try its’ best to ensure the pressure in the line will remain constant no matter what the flow rate is, so (with leaking through the tubing) the flow rate out of the CO2 regulator would increase in order to keep the output pressure constant, and that is all that would change. It would work like a soaker hose for the yard. That type of hose leaks a lot of water through little pinholes along its’ length, but you can still easily hook up a spray nozzle to the far end and use it just like a normal hose if you wanted to without noticing any real difference in flow through the spray nozzle.
Have a good one, Jeremy
P.S.- I heard that you can lose up to 20% of your dissolved CO2 in an acrylic aquarium through the acrylic itself, so everyone should use glass tanks if they want to successfully grow plants. It was a very interesting tidbit of information that my local glass aquarium manufacturer told me. I have troubles growing plants sometimes, so I think I am going to go out and buy a glass aquarium to replace my acrylic one and see if that helps. Ouch, I think I just bit my tongue. I guess I shouldn’t stick it so far into my cheek and then bite down on it, haha.
P.S.S.- I just wanted to add that I am in no way making fun of the original starter of this thread. It was a great question and I am really glad the question was asked, because I was able to learn something that I wasn’t totally sure about before now, and I am always grateful to anyone that can help me to grow in wisdom. Hopefully this helps someone else too. Maybe now some other people that really enjoy this hobby and who might be short on money can save a little bit of what they do have by not bothering with buying (or wondering if they need) the more expensive tubing for their CO2 systems.
P.S.S.- If anyone sees that my calcs are off, to the point that the conclusion that Vaughn and I have now both drawn might be wrong, let me know. I don't want to be spreading false info just because I accidentally made a mistake in my math.
I just posted that link to the table, because I already had the link bookmarked on my browser. I originally saved the link because I was looking into designing a CO2 distribution manifold for feeding multiple tanks and I wanted to see what my diffusive losses would be if I ended up using around 15’ of ½” SCH40 PVC.
I used the PVC value from the table I linked to, 0.06cc for my bubble size, the exact actual ID and OD of SCH40 ½” PVC, 10psi as my line pressure, 20bubbles/sec as my flow rate, the pipe outside diameter for calculating the total surface area, etc. With that bubble rate of CO2 flowing for 24 hours a day I came up with a loss of 0.009% of my total CO2. I breathe out more CO2 than that with every breath I take, so needless to say I was happy with that result, and I will be using PVC for my future distribution manifold.
I never did the calcs for tubing since my tubing is always running at 1psi or less I never thought it would make a difference one way or the other. That’s why I just use regular vinyl airline for my setup, instead of anything “CO2 proof”. I just kept the lengths of airline short just in case I realized later that I was wrong in my assumption and it did in fact leak a noticeable percentage of CO2, haha.
You caught me though Vaughn, you reeled me in with your post. I felt compelled to take your challenge and try the calcs again, only for the tubing losses this time. I only did two calcs though. I figured what would possibly be the worst-case scenario for any planted tank setup. I calculated for a 10’ long tubing run, silicone tubing, 5 bubbles per second flow rate, 0.06cc bubble size, and 10psi pressure within the silicone tube. The only area (that I know of as of now) I might be in error with my calcs was in calculating the surface area of the tubing. I didn’t know whether the tubing inside surface area was what mattered, outside surface area, or possibly the average of the two. I used the average of the two. I also couldn’t find a specific ID and OD for silicone tubing, so I used the values of 3/16” ID and ¼” OD (which is the ID and OD for regular vinyl airline) instead.
I found that with the aforementioned specs I ended up with a CO2 loss of 0.54%. That was with the worst possible tubing material of them all by far in as far as permeability (silicone), 10’ length, 5 bubble per second flow rate, and 10psi of pressure in the tubing.
I then realized that the losses might actually be worse with lower flow rates, so I recalculated it for a 1 bubble per second flow rate instead. I ended up with a loss calculation of 0.81% of total CO2.
Those situations both greatly exceed the conditions that 99% of us are using the tubing for, so in my opinion I agree with you Vaughn, there is no real benefit to using special “CO2 proof” tubing.
I guess this CO2 leakage thing is really possibly just a rumor that was started by the people that make the “good” stuff in order to sell more expensive tubing.
I would be a little careful about using something like that as proof of your calculations though. CO2 could be leaking through the tubing quite fast and still just be dissolving directly into the water without ever first forming bubbles on the sides of the tubing (i.e. semipermeable membrane technology for diffusing CO2 directly into water). You can also leak a lot of CO2 through the tubing and still have the exact same pressure at the end of the line. The CO2 pressure regulator will try its’ best to ensure the pressure in the line will remain constant no matter what the flow rate is, so (with leaking through the tubing) the flow rate out of the CO2 regulator would increase in order to keep the output pressure constant, and that is all that would change. It would work like a soaker hose for the yard. That type of hose leaks a lot of water through little pinholes along its’ length, but you can still easily hook up a spray nozzle to the far end and use it just like a normal hose if you wanted to without noticing any real difference in flow through the spray nozzle.
Have a good one, Jeremy
P.S.- I heard that you can lose up to 20% of your dissolved CO2 in an acrylic aquarium through the acrylic itself, so everyone should use glass tanks if they want to successfully grow plants. It was a very interesting tidbit of information that my local glass aquarium manufacturer told me. I have troubles growing plants sometimes, so I think I am going to go out and buy a glass aquarium to replace my acrylic one and see if that helps. Ouch, I think I just bit my tongue. I guess I shouldn’t stick it so far into my cheek and then bite down on it, haha.
P.S.S.- I just wanted to add that I am in no way making fun of the original starter of this thread. It was a great question and I am really glad the question was asked, because I was able to learn something that I wasn’t totally sure about before now, and I am always grateful to anyone that can help me to grow in wisdom. Hopefully this helps someone else too. Maybe now some other people that really enjoy this hobby and who might be short on money can save a little bit of what they do have by not bothering with buying (or wondering if they need) the more expensive tubing for their CO2 systems.
P.S.S.- If anyone sees that my calcs are off, to the point that the conclusion that Vaughn and I have now both drawn might be wrong, let me know. I don't want to be spreading false info just because I accidentally made a mistake in my math.
Vaughn,
I just posted that link to the table, because I already had the link bookmarked on my browser. I originally saved the link because I was looking into designing a CO2 distribution manifold for feeding multiple tanks and I wanted to see what my diffusive losses would be if I ended up using around 15’ of 1/2” SCH40 PVC.
I used the PVC value from the table I linked to in my above post, 0.075cm3 for a very close estimate of my bubble size (I measured how many bubbles of CO2 my system took to fill up exactly 15mL and then divided from there to find out how many cm3 each bubble was), the exact actual inside diameter of SCH40 1/2” PVC for calculating the surface area across which diffusion would occur, 10psi as my line pressure, 20bubbles/sec as my flow rate, etc. With that bubble rate of CO2 flowing for 24 hours a day I came up with a loss of 0.0019% of my total CO2. I was happy with that result, so I will be using PVC for my future distribution manifold.
I never did the calcs for tubing since my tubing is always running at 1psi or less I never thought it would make a difference one way or the other. That’s why I also just use regular vinyl airline for my setup, instead of anything “CO2 proof”. I just kept the lengths of airline short just in case I realized later that I was wrong in my assumption and it did in fact leak a noticeable percentage of CO2, haha.
You caught me though Vaughn, you reeled me in with your post. I felt compelled to take your challenge and try the calcs again, only for tubing this time. I did a few calcs and I will present them here. I figured what would possibly be the worst-case scenario for any planted tank CO2 system, and then also did what I think is a very likely setup.
Worst-case scenario stuff-
Silicone tubing- 10’ long, at 10psi pressure, 4mm inside diameter, 6mm outside diameter, and 5 bubbles/sec. flow rate of CO2 into the aquarium 24 hrs a day.
You would lose about 3409cm3 of CO2 in 24hrs. 5 bubbles a second ~ 32400cm3 in 24 hrs, so that would be about 10.5% of your CO2 lost through the silicone airline. That is a sizable number, but remember that is running the system at 10psi.
Regular vinyl tubing- 10’ long, at 10psi pressure, 3/16” inside diameter, 1/4" outside diameter, and 5 bubbles/sec. flow rate of CO2 into the aquarium 24 hrs a day.
You would lose about 91.44cm3 of CO2 in 24hrs. 5 bubbles a second ~ 32400cm3 in 24 hrs, so that would be about 0.28% of your CO2 lost through the vinyl airline.
0.28% is very low, and that is at 10psi, so I am not going to keep calculating regular vinyl airline anymore, because the losses are already too low to bother worrying about. I will do one more calculation, the losses through a very common planted tank setup scenario that uses silicone tubing (which is the worst of all tubing types by a large margin in as far as CO2 escaping through the tubing).
A very likely planted tank type setup using silicone tubing-
Silicone tubing- 4’ long, at ~1psi pressure, 4mm inside diameter, 6mm outside diameter, and 3 bubbles/sec. flow rate of CO2 into the aquarium 24 hrs a day.
You would lose about 136cm3 of CO2 in 24hrs. 3 bubbles a second ~19440cm3 in 24 hrs, so that would be about 0.70% of your CO2 lost through the silicone airline.
I think this shows clearly that CO2 leakage through the tubing itself can be a real issue at higher pressures (especially with silicone tubing), but under the conditions all of us will be using the tubing (1-2psi max) it is really a non-issue.
I would be a little careful about using something like that as proof of your calculations. CO2 could be leaking through the tubing quite fast and still just be dissolving directly into the water without ever first forming bubbles on the sides of the tubing (i.e. semi-permeable membrane technology for diffusing CO2 directly into water). You can also leak a lot of CO2 through the tubing and still have the exact same pressure at the end of the line. The CO2 pressure regulator will try its’ best to ensure the pressure in the line will remain constant no matter what the flow rate is, so (with leaking through the tubing) the flow rate out of the CO2 regulator would increase in order to keep the output pressure constant, and that is all that would change. It would work like a soaker hose for the yard. That type of hose leaks a lot of water through little pinholes along its’ length, but you can still easily hook up a spray nozzle to the far end and use it just like a normal hose if you wanted to without noticing any real difference in flow through the spray nozzle.
Have a good one, Jeremy
P.S.- If anyone tries to repeat my calcs and reproduce my findings for themselves and realizes that my calcs are off, to the point that the conclusion that Vaughn and I have now both drawn might be wrong, let me know and if I realize/agree that I made a mistake I will correct it. I don't want to be spreading false info just because I accidentally may have made a mistake in my math.
I just posted that link to the table, because I already had the link bookmarked on my browser. I originally saved the link because I was looking into designing a CO2 distribution manifold for feeding multiple tanks and I wanted to see what my diffusive losses would be if I ended up using around 15’ of 1/2” SCH40 PVC.
I used the PVC value from the table I linked to in my above post, 0.075cm3 for a very close estimate of my bubble size (I measured how many bubbles of CO2 my system took to fill up exactly 15mL and then divided from there to find out how many cm3 each bubble was), the exact actual inside diameter of SCH40 1/2” PVC for calculating the surface area across which diffusion would occur, 10psi as my line pressure, 20bubbles/sec as my flow rate, etc. With that bubble rate of CO2 flowing for 24 hours a day I came up with a loss of 0.0019% of my total CO2. I was happy with that result, so I will be using PVC for my future distribution manifold.
I never did the calcs for tubing since my tubing is always running at 1psi or less I never thought it would make a difference one way or the other. That’s why I also just use regular vinyl airline for my setup, instead of anything “CO2 proof”. I just kept the lengths of airline short just in case I realized later that I was wrong in my assumption and it did in fact leak a noticeable percentage of CO2, haha.
You caught me though Vaughn, you reeled me in with your post. I felt compelled to take your challenge and try the calcs again, only for tubing this time. I did a few calcs and I will present them here. I figured what would possibly be the worst-case scenario for any planted tank CO2 system, and then also did what I think is a very likely setup.
Worst-case scenario stuff-
Silicone tubing- 10’ long, at 10psi pressure, 4mm inside diameter, 6mm outside diameter, and 5 bubbles/sec. flow rate of CO2 into the aquarium 24 hrs a day.
You would lose about 3409cm3 of CO2 in 24hrs. 5 bubbles a second ~ 32400cm3 in 24 hrs, so that would be about 10.5% of your CO2 lost through the silicone airline. That is a sizable number, but remember that is running the system at 10psi.
Regular vinyl tubing- 10’ long, at 10psi pressure, 3/16” inside diameter, 1/4" outside diameter, and 5 bubbles/sec. flow rate of CO2 into the aquarium 24 hrs a day.
You would lose about 91.44cm3 of CO2 in 24hrs. 5 bubbles a second ~ 32400cm3 in 24 hrs, so that would be about 0.28% of your CO2 lost through the vinyl airline.
0.28% is very low, and that is at 10psi, so I am not going to keep calculating regular vinyl airline anymore, because the losses are already too low to bother worrying about. I will do one more calculation, the losses through a very common planted tank setup scenario that uses silicone tubing (which is the worst of all tubing types by a large margin in as far as CO2 escaping through the tubing).
A very likely planted tank type setup using silicone tubing-
Silicone tubing- 4’ long, at ~1psi pressure, 4mm inside diameter, 6mm outside diameter, and 3 bubbles/sec. flow rate of CO2 into the aquarium 24 hrs a day.
You would lose about 136cm3 of CO2 in 24hrs. 3 bubbles a second ~19440cm3 in 24 hrs, so that would be about 0.70% of your CO2 lost through the silicone airline.
I think this shows clearly that CO2 leakage through the tubing itself can be a real issue at higher pressures (especially with silicone tubing), but under the conditions all of us will be using the tubing (1-2psi max) it is really a non-issue.
I would be a little careful about using something like that as proof of your calculations. CO2 could be leaking through the tubing quite fast and still just be dissolving directly into the water without ever first forming bubbles on the sides of the tubing (i.e. semi-permeable membrane technology for diffusing CO2 directly into water). You can also leak a lot of CO2 through the tubing and still have the exact same pressure at the end of the line. The CO2 pressure regulator will try its’ best to ensure the pressure in the line will remain constant no matter what the flow rate is, so (with leaking through the tubing) the flow rate out of the CO2 regulator would increase in order to keep the output pressure constant, and that is all that would change. It would work like a soaker hose for the yard. That type of hose leaks a lot of water through little pinholes along its’ length, but you can still easily hook up a spray nozzle to the far end and use it just like a normal hose if you wanted to without noticing any real difference in flow through the spray nozzle.
Have a good one, Jeremy
P.S.- If anyone tries to repeat my calcs and reproduce my findings for themselves and realizes that my calcs are off, to the point that the conclusion that Vaughn and I have now both drawn might be wrong, let me know and if I realize/agree that I made a mistake I will correct it. I don't want to be spreading false info just because I accidentally may have made a mistake in my math.
I may do some more manipulating of this, but probably not. One thing that might affect the answer is the value of the pressure inside the tubing. Since the tube contains virtually pure CO2, if the loss is proportional to partial pressure difference across the material, that gives about 15 psi differential pressure. But, if the loss is proportional to the total pressure differential across the material, you get very close to zero pressure diferential - the presssure should be roughly equal to the depth of the end of the CO2 tube in the tank water, a few inches of water or around 0.1 psi. The calculated loss for the two interpretations is obviously very different. I don't know which is the correct one.
The main issues are distance the CO2 travels, the thickness of the tubing involved, pressure is a huge factor and the temp.
I really do not think you lose much either way.
I think it's more a marketing deal to sell $$$$ tubing.
I like good sticky thick walled tubing that stays flexible.
This prevents real leaks, not the marketing leaks.
A 10% CO2 tank loss cost you 2$ based on a rather high 20$ refill.
Now at 1-2$ per ft, vs say .20 cent a foot, it'll take a few years to off set the cost if you have say 10-20ft of tubing.
Still, chicken feed $, but hardly worth discussing further..........you could make more $ sitting here than you'd save
Regards,
Tom Barr
I really do not think you lose much either way.
I think it's more a marketing deal to sell $$$$ tubing.
I like good sticky thick walled tubing that stays flexible.
This prevents real leaks, not the marketing leaks.
A 10% CO2 tank loss cost you 2$ based on a rather high 20$ refill.
Now at 1-2$ per ft, vs say .20 cent a foot, it'll take a few years to off set the cost if you have say 10-20ft of tubing.
Still, chicken feed $, but hardly worth discussing further..........you could make more $ sitting here than you'd save
Regards,
Tom Barr
Tom Barr;30028 said:Still, chicken feed $, but hardly worth discussing further..........you could make more $ sitting here than you'd save
Regards,
Tom Barr
Is my check in the mail??
Tom,
Thanks for bringing that up Tom, I forgot to ever mention the temperature aspect of the calcs. The table from the link is only valid for I think 25 degrees Celsius if I remember correctly. The farther you get from that temp the more off the calcs will be. I don't know how much they will change though becuase the temperature factor is factored into the diffusion value from the table and is not part of the calcs I can do unless I could find a new table with temperature adjusted diffusion values. I am not motivated enough to look for that, so I will just leave well enough alone. My biggest aquarium issues right now are not CO2 tubing loss related anyways, haha.
Vaughn,
The pressure of the CO2 within the tubing is one of the factors that you have to plug in when trying to find the CO2 loss through the tubing. More pressure = more loss. I didn't show my work before, but I calculated the loss my multiplying (total surface area of tubing for a given length in cm2) x ([HASHTAG]#seconds[/HASHTAG] in a day) x (1/ tubing wall thickness in mm) x (gauge pressure of CO2 within tubing converted to cmHg) x (permeability constant from table provided in my first post x 10-10) = [HASHTAG]#cm3[/HASHTAG] CO2 lost within a 24 hour period.
The bubble rate that you are flowing actually makes no difference other than to use as a measuring stick to find your particular CO2 loss %. For instance, if you calculated a loss of 100cm3 a day and you kept the tubing pressurized but shut off at the end of the line so nothing was going into the aquarium (via a solenoid) you would still lose that 100cm3 CO2 a day through the tubing. If you were flowing 50 bubbles a second through the system into the tank you would still only be losing 100cm3 a day through the tubing. The loss amount is constant for all flow rates through the tubing as long as the line pressure remains consistent, which it would with loss levels that are as low as they are through the tubing and with flow levels as low as what we are running through our systems.
They both are correct. If you have tubing between your CO2 regulator output and the needle valve you would use the output pressure gauge on the regulator for calculating the CO2 loss through that length of tubing because that tubing is pressurized to the output pressure from the regulator at all times.
For any tubing after a needle valve (which cuts flow and creates a pressure drop) you would use the pressure required to push the bubbles down into the tank water and that's it, which would be 1psi for every 2.3' of depth the CO2 hose goes below the water surface. That pressure being so small is why this is really a non-issue for just about any setup that will be used for planted tanks. Most people only use tubing after the needle valve, so the pressure is always less than 1psi and often only a small fraction of 1psi.
Have a good one, Jeremy
Thanks for bringing that up Tom, I forgot to ever mention the temperature aspect of the calcs. The table from the link is only valid for I think 25 degrees Celsius if I remember correctly. The farther you get from that temp the more off the calcs will be. I don't know how much they will change though becuase the temperature factor is factored into the diffusion value from the table and is not part of the calcs I can do unless I could find a new table with temperature adjusted diffusion values. I am not motivated enough to look for that, so I will just leave well enough alone. My biggest aquarium issues right now are not CO2 tubing loss related anyways, haha.
Vaughn,
The pressure of the CO2 within the tubing is one of the factors that you have to plug in when trying to find the CO2 loss through the tubing. More pressure = more loss. I didn't show my work before, but I calculated the loss my multiplying (total surface area of tubing for a given length in cm2) x ([HASHTAG]#seconds[/HASHTAG] in a day) x (1/ tubing wall thickness in mm) x (gauge pressure of CO2 within tubing converted to cmHg) x (permeability constant from table provided in my first post x 10-10) = [HASHTAG]#cm3[/HASHTAG] CO2 lost within a 24 hour period.
The bubble rate that you are flowing actually makes no difference other than to use as a measuring stick to find your particular CO2 loss %. For instance, if you calculated a loss of 100cm3 a day and you kept the tubing pressurized but shut off at the end of the line so nothing was going into the aquarium (via a solenoid) you would still lose that 100cm3 CO2 a day through the tubing. If you were flowing 50 bubbles a second through the system into the tank you would still only be losing 100cm3 a day through the tubing. The loss amount is constant for all flow rates through the tubing as long as the line pressure remains consistent, which it would with loss levels that are as low as they are through the tubing and with flow levels as low as what we are running through our systems.
They both are correct. If you have tubing between your CO2 regulator output and the needle valve you would use the output pressure gauge on the regulator for calculating the CO2 loss through that length of tubing because that tubing is pressurized to the output pressure from the regulator at all times.
For any tubing after a needle valve (which cuts flow and creates a pressure drop) you would use the pressure required to push the bubbles down into the tank water and that's it, which would be 1psi for every 2.3' of depth the CO2 hose goes below the water surface. That pressure being so small is why this is really a non-issue for just about any setup that will be used for planted tanks. Most people only use tubing after the needle valve, so the pressure is always less than 1psi and often only a small fraction of 1psi.
Have a good one, Jeremy
And what types of diffusion per meter does lone get at say 25 C and 1 psi?
Probably not much.
So it's more for larger scale, higher pressure applications really, for it to be cost effective, why strain the brain for pennies here?
It' ain't worth it or your time. Unless you like straining the brain in diffusion and Fick's 1st law.
Regards,
Tom Barr
Probably not much.
So it's more for larger scale, higher pressure applications really, for it to be cost effective, why strain the brain for pennies here?
It' ain't worth it or your time. Unless you like straining the brain in diffusion and Fick's 1st law.
Regards,
Tom Barr
The only reason to strain our brains over this is that for months, if not years, it has been said, and is stil being said that using silicone tubing is a no-no for our CO2 lines, which are almost always the line from the needle valve to the diffuser (very low pressure). That table shows such a drastic difference in permeability between silicone and everything else that it is "obvious" that silicone tubing is truly bad with CO2.
But, after staining our brains a bit, it turns out that none of the permeabilities mentiioned are high enough to be a problem for CO2 lines downstream of the needle valve. Therefore, silicone tubing is very usable for our CO2 application. One more myth bites the dust!
But, after staining our brains a bit, it turns out that none of the permeabilities mentiioned are high enough to be a problem for CO2 lines downstream of the needle valve. Therefore, silicone tubing is very usable for our CO2 application. One more myth bites the dust!
Thanks for all the input guys. I did switch tubing, got the polyetholene only cost $2.50 for 30 feet so no breaking the pocket book,maybe I had a leak and the other stuff will seal better or whatever the case may be.
Tom,
I don't quite understand your seeming hostility toward Vaughn and I for voluntarily taking the time to investigate this myth and do the calcs necessary to figure out what the truth is. I can't speak for Vaughn, but personally I did this in hopes of possibly adding something meaningful and concrete to the site that has given me so much in other areas.
Just in case you or anyone else is wondering, the answer to this question from post #10
That was part of my original calcs and results from post #5
And also what you said about the following from post #10
Was the same conclusion I stated from post #5 (re-quoted below) and also again in post #9 as well, so we are all in agreement (and we actually always were), it is just that now there are some actual calcs to back up those opinions.
Quote from post #5
Quote from post #9
Have a good one, Jeremy
P.S.- I wrote this post solely as a clarification for anyone else that may be reading this. We are all in agreement here, and we always were in regards to "CO2 proof" tubing. There is no measurable benefit for our low-pressure applications, so unless you like the special types of tubing for other reasons, don't bother with it.
I don't quite understand your seeming hostility toward Vaughn and I for voluntarily taking the time to investigate this myth and do the calcs necessary to figure out what the truth is. I can't speak for Vaughn, but personally I did this in hopes of possibly adding something meaningful and concrete to the site that has given me so much in other areas.
Just in case you or anyone else is wondering, the answer to this question from post #10
That was part of my original calcs and results from post #5
And also what you said about the following from post #10
Was the same conclusion I stated from post #5 (re-quoted below) and also again in post #9 as well, so we are all in agreement (and we actually always were), it is just that now there are some actual calcs to back up those opinions.
Quote from post #5
Quote from post #9
Have a good one, Jeremy
P.S.- I wrote this post solely as a clarification for anyone else that may be reading this. We are all in agreement here, and we always were in regards to "CO2 proof" tubing. There is no measurable benefit for our low-pressure applications, so unless you like the special types of tubing for other reasons, don't bother with it.
Tom,
Just in case you missed it, I did almost that exact calculation and told the results in post #5 of this thread. I think we are all in agreement that it is a waste of money to buy "CO2 proof" tubing in order to prevent CO2 losses in our application.
Here is a reprint from post #5.
Have a good one, Jeremy
Just in case you missed it, I did almost that exact calculation and told the results in post #5 of this thread. I think we are all in agreement that it is a waste of money to buy "CO2 proof" tubing in order to prevent CO2 losses in our application.
Here is a reprint from post #5.
Have a good one, Jeremy