# dosing pump getting air in the lines



## ajm83 (17 Nov 2015)

My dosing pump keeps getting air in the lines. Line 1 is by far the worst:






I've taken the pump head off, can't see anything wrong (pinched or split lines), and this never happens when I run the pump manually (I ran it for a good 2 or 3 minutes with no air appearing).

Anyone know what's wrong? It's such a simple device I can't see what can be happening.

Thanks
A.


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## jagillham (17 Nov 2015)

How long before the line gets air in it, does this happen over time?

Assuming the end of the line is below the surface of the liquid at the bottom of the container?


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## ajm83 (17 Nov 2015)

Yes, it seems to happen over the course of a few days. Lines are indeed above the surface tank end, and at the bottom of the liquid in the macro dosing pot thingy. 

I've just heard back from the seller, he's going to send me a new pump head so I'll try that and update the thread if it makes a difference. 

Only thing I can think of is that either there is a very tiny hole in the squishy line somewhere inside the head, or the input of liquid is jamming and hence the pump is pulling dissolved gas out of the liquid (like if you pull really hard on the syringe when you're bleeding your brakes...!) 
Seems very unlikely in either case as it never happens when running the pump manually.


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## jagillham (17 Nov 2015)

If the seal is good and the pipe is at the bottom of the liquid - then my next guess would be the roller is not quite causing a vacuum as it goes around. New head should hopefully sort that one.

What make / model is that out of interest?


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## ajm83 (26 Nov 2015)

It's a Jebao DP4. So wasn't expecting the finest quality but was hoping for it to work!

The seller kindly sent a replacement head which I have fitted, but this hasn't solved the issue. Nor has adding more check valves. I just don't understand what is happening.

I can run it on manual for as long as I want with no bubbles. Come back the next morning and there are bubbles in the line! HOW?!! Unless all my lines have small holes, or both the old and replacement heads are faulty.


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## DTL (26 Nov 2015)

I would check the seals on the line connectors. I find that adding a small cable tie helps to seal these better.


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## ian_m (26 Nov 2015)

Put cable ties around your nipples...


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## ajm83 (26 Nov 2015)

Thanks both, I'll add some zip ties then.


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## jagillham (30 Nov 2015)

Does the problem still persist out of interest?


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## aaron.c (30 Nov 2015)

I am having the same issues.

I use CO2 tube as someone said airline was not suitable.

The other day my macro and micro doses stopped working all together - cue melting


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## ajm83 (30 Nov 2015)

Hi, still waiting for zip ties to turn up, I'll update the thread effect they're in and have been running for a few days. 
Cheers 

Sent from my A0001 using Tapatalk


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## ajm83 (9 Dec 2015)

Gah! Thought I'd cracked it with the zip ties, but low and behold, a cheeky bubble appeared in the line for the micros this morning. Think there might be a few tiddlers in the macros too.






Wondering now about removing the little plastic connectors and replacing them with checkvalves with the lines on pushed really hard. I pressure tested that setup previously and it went really high (> 150PSI) with no leaks. Hopefully it'll behave the same (a) with liquid and (b) under suction on the inlet side of the lines.


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## DTL (10 Dec 2015)

I'm not sure that you need the valves, and they might also be where the leaks are coming from. l'dd add the cable ties to those connections too.
Another thing to check is that your solution bottles are not air tight otherwise you will be trying to pull against a vacuum after a while, which would stress the connection points and pull air. Ensure that one of the lids allows airflow.


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## ajm83 (10 Dec 2015)

DTL said:


> I'm not sure that you need the valves, and they might also be where the leaks are coming from. l'dd add the cable ties to those connections too.
> Another thing to check is that your solution bottles are not air tight otherwise you will be trying to pull against a vacuum after a while, which would stress the connection points and pull air. Ensure that one of the lids allows airflow.



I'll double check the lids, but I think they are all unscrewed. 

I had the bubble problem before adding the check valves, at the time I thought the issue was due to backflow. 
I'm 99 % certain they cannot leak at the connections due to how physically hard it was to put the lines on them and the fact that they took so much pressure from my track pump without blowing, but I can remove them and see if it improves matters.

Andy.


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## ian_m (10 Dec 2015)

DTL said:


> I'm not sure that you need the valves, and they might also be where the leaks are coming from.


You only need the valves if your peristaltic pump is two roller. With a two roller the pump can stop in a position where the pipe is not squeezed shut and liquid can back flow down the pipe. With 3 roller (better with 4 roller) when the pump is stopped at least one roller will be squeezing the pipe shut, therefore backflow cannot occur.

How did you make your solutions ? If you used tap water, I bet it is dissolved gas coming out of solution when the pump produces reduced pressure in the pipe.

Try making the solutions using boiled tap water, as this will have been degassed. Just a thought.


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## JPT1974 (1 Jan 2016)

How's it going now ajm83? Did Ian's suggestion of degassing your water before making up your dosing solution work?


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## ajm83 (2 Jan 2016)

JPT1974 said:


> How's it going now ajm83? Did Ian's suggestion of degassing your water before making up your dosing solution work?



I'm still working through the current batch of macros, so it'll be a couple of weeks before I can try it.  I will update the thread when I do though!


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## JPT1974 (3 Jan 2016)

Ok. It's an interesting thread. All be it frustrating for you, sorry. Trouble shooting things like this though can help loads of other people. I hope to be setting up my TMC easidose shortly and have picked up a number of tips/ideas. Thank you


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## tmiravent (20 Jan 2016)

Hi,
i have the same doser and found some interesting stuff, maybe it help's...

Using Urea tend's to 'crystallize' inside the tube, regular cleaning of all tube is needed.
Using harder (Co2) it's worst. A smaller diameter and more elastic tube will fit better (in my case).
The small transparent plastic pieces that connect the tubes have rude finishing. Air can enter there sometimes (this would be the first thing to try IMO), get better connections.
Even that good non return valves tend to glue sometimes, check from time to time.
I have 3 pump's. the Jebao DP4, ATI DP6 (similar) and 1 channel growtech.
The last one is the better and most expensive!
The others work fine and the price is good (even with this small annoying things).
cheers


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## ajm83 (26 Jan 2016)

Okay so I finished my macros and made some up last week using boiled and partially cooled RO water. Unfortunately I've still got the bubbles appearing!

I still have hardly any bubbles appearing in the micros, so I guess I need to replace the pump head again.

btw Does anybody know of a really soft, clear tubing supplier I could use to run all the way from bottle, through the pump head to tank with no breaks? (I assume normal airline tubing would be too stiff to work?)


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## tmiravent (26 Jan 2016)

Hi,
try to change the small 'transparent plastic' join pieces,
this is my best guess!
take out cable ties, and try normal air tubbing.
cheers


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