# [Wet Thumb Forum]-Needle Valve Behavior



## Neight Goetz (Jan 5, 2004)

Hello

I had FINALLY purchased a compressed CO2 system, after running DIY for 6 years.
I havn't got the adjustments with the needle valve to where I want them yet. Here's my system:
Tank/reg/inline needlevalve(fabco)/(No Check valve)/Eheim diffuser.
It looks like I have ~2.5 bubbles a sec, then i'll check later that night and i'll be at .5 bubbles a second. It seems if I hardly turn the valve i'll get a great increase in bubbles per second. Is that how a needle valve is suppose to work? Do I have to wait several hours to see what the final results are, or do I just have a real sensitive needle valve?

N8


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## Neight Goetz (Jan 5, 2004)

Hello

I had FINALLY purchased a compressed CO2 system, after running DIY for 6 years.
I havn't got the adjustments with the needle valve to where I want them yet. Here's my system:
Tank/reg/inline needlevalve(fabco)/(No Check valve)/Eheim diffuser.
It looks like I have ~2.5 bubbles a sec, then i'll check later that night and i'll be at .5 bubbles a second. It seems if I hardly turn the valve i'll get a great increase in bubbles per second. Is that how a needle valve is suppose to work? Do I have to wait several hours to see what the final results are, or do I just have a real sensitive needle valve?

N8


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## gsmollin (Feb 3, 2003)

I have no personal experience with the Fabco needle valve, so I can't say if that is how they work. However, I can tell you a lot about needle valves, and how they should work. You should have your regulator set at 12-15 psi. The needle valve should be placed close to the bubble counter. This is so that you can quickly see the results of turning the needle valve. If you have several feet of tubing between the needle valve and the counter, you may have to wait several minutes for the changes in the needle valve to settle at the bubble counter. The mass of gas in the tubing causes the delay, and will make settings very difficult.

Making the adjustment is your next trick. First off, be prepared for a very touchy adjustment. For years I used a small needle valve, the Clippard MNV-4K2, the best one I know of, and I had to make the adjustment by gripping the adjustment knob with a needle-nosed pliars so that I had enough movement control for the microscopic adjustment it needed. I haven't tried the Fabco, but I can imagine it is no better. Another point is to adjust the valve by tightening it only. If you undershoot the adjustment, you must back-off the valve, say, a turn, and start the adjustment all over again. This eliminates the effects of backlash in the thread. Finally, understand that most needle valves are too coarse for this application. They are intended for at least 10 times the flow-rates we aquarists use them at. A better kind of valve for this application is called a fine-precision-metering valve. If you use one of them, then you will be able to turn the knob and move to a new flow rate without a struggle. However, they are more expensive than what you already have. You should work with what you bought to see if it is useable. You might want to contact your supplier and give him some feedback as well. Sometimes the valves need to be replaced from new.


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## imported_Brett (Jul 23, 2003)

Hi Neight,

Can I please suggest strongly that you put a check valve inline (tank side of the needle valve). I once ran out of CO2 and there was no pressure to hold the water back and I managed to syphon a significant amount of water down into my CO2 cylinder. It caused the internals of my regulator to rust









On the needle valve itself I can't comment although it sounds like a real pain in the butt. I have a complete Dupla pH-Control Detla (I am blessed with more money than sense), and the needle valve is great. The control is quite fine although nothing like what you guys are talking about.

The only thought that I have came from gsmollin's post and that might be CO2 pressure. Perhaps you have too much pressure in the line? That would certainly account for the symptoms that you're describing. Again though I'm guessing as my system uses a fixed reg that is preset to 1 bar (don't know off the top of my head how that relates to the 12-15psi that gsmollin mentioned)


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## IUnknown (Feb 24, 2004)

One other thing that happened to me was a Co2 line leak. I had a leak right where the tubbing bent into the tank. I thought my needle valve was broken because it was acting really strange, I even bought a new one. When it still had the same problem I dipped all my tubbing under water to see if I had leaks.

*Journal Database*


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## ekim (Jan 31, 2004)

All great suggestions!

One more,
Once you get the bubble rate close to what you want, you can fine tune it by slightly adjusting the regulator pressure.

By doing this I can adjust my bubble count by 1 bubble per minute!

Regards,
Mike Morrissey

---------------
*My Digital Gallery*


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## Neight Goetz (Jan 5, 2004)

I had my reg set at ~25psi...
so I cranked it down to 15psi.
Things are stable now.

Thanks!!

N8


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## freshwater1955 (Sep 15, 2009)

*user manual--dupla ph control MP*

Hi can somebody help me with a copy of the user manual for the dupla ph control MP unit ?
TIA


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