# CO2 Bubble Counter Problem with One-way value



## 30searay (May 1, 2007)

I have recently set up a 110 gallon complete with the pressurized CO2 system from Dr. Foster and Smith. The system is of good quality except for the bubble counter. When the pH drops to the prescribed level on the low side reading of the pH controller it shuts off the system as it should. However, once the solenoid shuts off flow from the Co2 tank, pressure builds up in the Co2 airtube line from the reacor to the bubble counter. This appears to be due to the water that continues to circulate through the reactor (as the water pump continues to run all the time). I have just blown the second one-way value in my bubble counter, water then fills the bubble counter leaks around the value inlet and runs down the CO2 line towards the solenoid and the tank. Is this just a cheap quality bubble counter (complete with plastic one-way valve)? Are brass valves available with bubble counters or, more likely, am I just doing something wrong?


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## furballi (Feb 2, 2007)

I've never worked with that design, so I cannot provide a solution. I suspect that your regulated pressure is too high. Running the CO2 24/7 to maintain the desired CO2 level will probably yield greater consistency in pH. Start out with 1 bubble per second and gradually increase as required to maintain 15 to 20 ppm of CO2.

All you need is a regulator, a quality $20 needle valve, and a one way stop valve to protect the needle valve from the tank's water. There is no need to set the regulated pressure above 10 psig with this setup.

You'll pay an extra $15 in CO2 per year with 24/7 injection, but you'll probably never have to worry about equipment failure or maintenance of the pH probe.


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## Rex Grigg (Jan 22, 2004)

It's not CO2 causing the problem. It's water creeping back up the tubing. This is quite common. Once you shut off the flow of CO2 the water will creep up the tubing and dissolve the CO2. It's not even an actual pressure problem. 

Best advice is to get a quality check valve and put it inline between the reactor and the bubble counter.


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## snickle (Apr 8, 2007)

I agree get a good check valve. Rex sells them on his site. They are what I use.


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## furballi (Feb 2, 2007)

Rex Grigg said:


> It's not CO2 causing the problem. It's water creeping back up the tubing. This is quite common. Once you shut off the flow of CO2 the water will creep up the tubing and dissolve the CO2. It's not even an actual pressure problem.
> 
> Best advice is to get a quality check valve and put it inline between the reactor and the bubble counter.


"Water creeping back up the tubing" is a "pressure problem"! It's covered under Physics 101. Higher regulated CO2 pressure will intensify this problem when the soleloid switches ON/OFF. It's hard to beat 24/7 injection if *your goal* is to maintain a stable pH.


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## Left C (Jun 14, 2005)

30searay said:


> ...The system is of good quality except for the bubble counter...


I installed one of those Aqua-Medic Bubble counters last week. It's a POS, IMO. Mine leaked CO2 in several places.

-One was around the blue exhaust elbow. It wasn't screwed on tight enough. CO2 was leaking through the threads.

-Another was where the intake tubing attached to the barbed intake on the top of the regular. This is the tubing between the cheap plastic check valve and the top of the regulator. The inner diameter was too large and stretched out. It fit really loose. I didn't try to cut the stretched out part off. I figured if it did it one time; it'll do it again. I had to remove this tubing and the check valve and replace the tubing with tighter fitting tubing. I had an extra brass check valve that I used as well. I didn't use the plastic check valve.

-When you take the top off to add water or glycerin on the inside, you have to make sure that the O-ring is in place and that the top is all the way down when you put the top back on or it will leak.

-Another thing is that you have to be careful when you adjust the needle valve on the regulator. You can blow the top off of the bubble counter if you open the needle valve up to a fairly high rate.

I thought that Aqua-Medic's products are good, but this thing isn't. I won't buy another.


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## furballi (Feb 2, 2007)

Left C said:


> I installed one of those Aqua-Medic Bubble counters last week. It's a POS, IMO. Mine leaked CO2 in several places.
> 
> -One was around the blue exhaust elbow. It wasn't screwed on tight enough. CO2 was leaking through the threads.
> 
> ...


A high quality Fabco NV55 needle valve should provide LINEAR response from zero flow to 80% full flow. The heart and soul of any CO2 injection rig is the needle valve. I suspect 99% of these end-of-tank dumping issues are caused by a poor needle valve. I think the NV55 is still Made in USA. I received my sample unit from a local distributor in S Cal. Unit cost is between $10 to $20.


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## Left C (Jun 14, 2005)

My post is about a lousy bubble counter that 30searay and I have. I was wanting to help 30searay out. I believe that you mentioned that you weren't familiar with it. 

Thanks for the info about a needle valve but I cranked mine up on purpose just to see if this lousy bubble counter still leaked. It was funny when it blew it's top.


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## Rex Grigg (Jan 22, 2004)

furballi:

If you can tell me where I can get the NV-55 for $10 each I would appreciate it.

But in this case pimping a new needle valve has nothing to do with the leaking bubble counter.

And you really should head back to Physics 101 as water creeping up CO2 tubing has NOTHING to do with pressure. But more to do with absorption of the CO2 gas.

If one were to pressurize tubing that had no leaks or diffusion though the walls of the tubing with air and use this tubing to inject air into a water column and then shut off the flow of air the level of water in the tubing vs the level of air would remain fairly static.

However since CO2 is readily absorbed into water water will dissolve the CO2 at the air CO2 interface and creep up the tubing.


And in this case the use of the supplied tubing only makes matters worse since the supplied silicone tubing leaks most all gases like a sieve.


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## furballi (Feb 2, 2007)

Rex Grigg said:


> furballi:
> 
> If you can tell me where I can get the NV-55 for $10 each I would appreciate it.
> 
> ...


Okay...take a chair Grass Hopper. If the pressure in the CO2 line is in equilibrium (pull out your dictionary) with the pressure exerted by the water column, then the water WILL NOT flow into the CO2 line. When pressure in the CO2 line is less than the pressure exerted by the water column, then water will flow into the CO2 line. There are MANY factors that could lower the pressure in the CO2 line, CO2 absorption being one of them! The ROOT CAUSE is the pressure differential (P1<P2).

As for the $10 price, there are a few distributors S Cal with volume discount.


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## Rex Grigg (Jan 22, 2004)

Nope. Been there done that. It's the water absorbing the CO2. If it was pressure you would not be able to back the CO2 all the back up to a check valve. At some point the water would pressurize the CO2 to the point where the water would no longer back up. You can even have the water climb up a the tubing a couple of feet. If it were mere pressure you would not have that. But the water absorbing the CO2 creates a vacuum in the line.

And since you have stated that you run your CO2 24/7 you would not have experienced this.

Please point me to a S Cal distributor with a volume discount to where I can get the NV55 for $10. Be specific. I am buying 25 at a time right now and am not even close to that price. I just checked the Fabco web site and see only four distributors in the whole state of California. So please point me to which one will sell the NV55 for $10.


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