Reoccurring air in the dosing line
- Thread starter Ziggy17
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Its not leaking from the pump, it just may be that the pump head rollers don’t seal tightly against the tubing enough to prime the line. So you get a few bubbles from the beginning of the line that gets caught in the tubing going around the pump head and never gets worked out.
For what it's worth, you would need to dose 3 inches of air (in a 4mm ID pipe), to reduce actual Alk dosing by 1 ml. Assuming that's not happening?
Are these your containers
Following. I’ve been having the same problem. But for me it is the Calcium solution that gets the air, ALK seems much better. Have tried checks, different connectors, etc. Very frustrating. I am using GHL dosers from Simplicity tanks. I am using that soft Simplicity tubing… not sure if that causes issues.
I have wondered if it is due to very small doses. Right now I have mine set for 3ml every hour. Perhaps 6ml every 2 hrs would do better or even dose just a couple times in the evenings… I primed the crap out of both lines, but still have the issue that you are experiencing.
I have wondered if it is due to very small doses. Right now I have mine set for 3ml every hour. Perhaps 6ml every 2 hrs would do better or even dose just a couple times in the evenings… I primed the crap out of both lines, but still have the issue that you are experiencing.
I have two. I have the same issue. Ive primed many times and I’ve replaced all the air line. I’ve also added check valves. I’m not sure what’s going on. I’m dosing sodium bicarbonate mix
I suspect crappy nipple connection on the container. Read reviews and people mention replacing /sealing the fittings
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Ziggy17
Well-Known Member
I actually bypassed the nipple and have the tubes directly in and still the same issue.
I had to deal with two issue to get rid of my bubbles.
1. If you are using common silicone tubing, it is likely the high permeability of silicone is allowing gas exchange. Especially if there is a constant suction in the line due to the pump being higher than the reservoir.
I had the same issue with a 7 ft run of tubing. Changed to clear FEP tubing and it worked perfect. But this tubing is somewhat stiff, and not easy to work with. I also use Python Air Line Tubing (PVC?) with success.
2. Nipple leaks drove me crazy. The nipples may have small surface irregularities from molding that leak. I was initially using an air line that was harder, and was leaking at the nipples. Between dosing cycles there would be air entering the line. The best tubing I found so far is Python Air Line Tubing. It’s softer, and seals very well.
My only concern with using air line tubing for dosing is the compatibility with the dosing chemicals. With that said, ICP testing is always clean, and I have no reason to believe it’s not compatible.
1. If you are using common silicone tubing, it is likely the high permeability of silicone is allowing gas exchange. Especially if there is a constant suction in the line due to the pump being higher than the reservoir.
I had the same issue with a 7 ft run of tubing. Changed to clear FEP tubing and it worked perfect. But this tubing is somewhat stiff, and not easy to work with. I also use Python Air Line Tubing (PVC?) with success.
2. Nipple leaks drove me crazy. The nipples may have small surface irregularities from molding that leak. I was initially using an air line that was harder, and was leaking at the nipples. Between dosing cycles there would be air entering the line. The best tubing I found so far is Python Air Line Tubing. It’s softer, and seals very well.
My only concern with using air line tubing for dosing is the compatibility with the dosing chemicals. With that said, ICP testing is always clean, and I have no reason to believe it’s not compatible.
No. Just no. There is no as exchange through silicone via suction. End of story. I work with these pumps in the pharmaceutical industry and platinum cured silicone is the gold standard for fluid transfers. It is considered an impermeable sterile barrier. There is no gas exchange.
Fair enough, I certainly yield to your expertise. I can only speak from a point of experience when I had a similar issue, and suspected the permeability of the tubing. A Google search returned that silicon has high relative permeability. Example:
“Silicone rubber has many characteristics which have enabled it to achieve wide use. Its vapour permeability, however is extremely high which leads to both specific benefits and considerable drawbacks in many applications. It is an excellent barrier against liquids, but many vapours – such as oxygen, water vapour and hydrogen can pass through most types of silicone almost as if it was not there. This makes it highly suitable for use in some applications, and totally unsuitable for others”
When I changed the tubing to FEP, the problem went away. But I’m pretty sure I was not using pharmaceutical grade platinum cured silicone tubing.
If the mechanism is not gas exchange, then I do not know the reason why the bubbles disappeared. Could it be that I simply had poor quality silicone or it was somewhat porous tubing?
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Ziggy17
Well-Known Member
For what it’s worth, there are gas bubbles forming from the 4’ run of tubing from the reservoir to the pump. The air is 100% not in the pump. It’s not the nipple as I’ve bypassed the nipple. The pockets start only a few inches up from the reservoir.
It has to be one of two things;
Silicone is allowing gas exchange
Or
The solution itself is degassing (not sure if that’s the correct term) inside the airline causing the pockets.
Perhaps those two are the same thing. I’m not a chemist or a physicist so I don’t know. In my head they are separate issues. Maybe the same issue.
I cannot see any other culprit occurring in that first 4’ of tubing.
It has to be one of two things;
Silicone is allowing gas exchange
Or
The solution itself is degassing (not sure if that’s the correct term) inside the airline causing the pockets.
Perhaps those two are the same thing. I’m not a chemist or a physicist so I don’t know. In my head they are separate issues. Maybe the same issue.
I cannot see any other culprit occurring in that first 4’ of tubing.
I will admit when I am wrong. Silicone is gas permeable. It is a sterile barrier, which I confused in my head with gas permeability. However, I still think it very unlikely that you could have enough gas exchange at the molecular level to observe on the macro scale as a bubble in the line.
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Ziggy17
Well-Known Member
Changing the tubing resolved the issue. I went from a very flexible style tubing to a more rigid tubing and it’s been 48 hours and no air in the lines, where prior bubbles would form within a few hours.
Hopefully this helps any others out there that are experiencing similar issues.
Hopefully this helps any others out there that are experiencing similar issues.
Interesting. Glad this solved your problem. Since rigid tubing seems to help, folks may also like to know that you can use 1/4 inch RODI tubing with the standard airline connectors on most dosing pumps. You just have to heat up the tubing to slip it over the barb. I made a video a while back:
I used this method to connect RODI tubing to my DOS pump instead of the flexible tubing it comes with. I did it to prevent kinks and for aesthetic reasons, but maybe it can help with trapped air issues too.
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Ziggy17
Well-Known Member
Interesting. Glad this solved your problem. Since rigid tubing seems to help, folks may also like to know that you can use 1/4 inch RODI tubing with the standard airline connectors on most dosing pumps. You just have to heat up the tubing to slip it over the barb. I made a video a while back:
I used this method to connect RODI tubing to my DOS pump instead of the flexible tubing it comes with. I did it to prevent kinks and for aesthetic reasons, but maybe it can help with trapped air issues too.
That’s actually a great idea as it does look much better than the tubing I used. At least now I don’t have to babysit my doser anymore. Was kinda defeating the purpose haha
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