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Re: Compressed Bottles/Regulators

> Hi there,
>             I have three questions for you about CO2 compressed bottle
> and
> pressure regulator.
> Well I bought a compressed bottle of 1Kg with a pressure regulator and
> two
> pressure manometers yesterday. Now my questions are:
> 1 I can read a pressure of 51 atm (750 psi) coming from the bottle but
> after the regulator I have no pressure reading in the outlet. The
> manometer
> on the outlet has a scale from 0 to 3 atm  but nothing moves even if the
> CO2 is coming out and entering in my CO2 bell very fast.
> Is this normal? I mean is it normal that I have no pressure after the
> regulator?

Yes, this is normal if there is not real back-pressure on the regulator.

> 2.I cannot set a right flow rate because after setting something like 1
> bubble every two seconds I wait 5 minutes and the flow stops and I have
> to
> turn again the valve and set it again to 1/2 bps
> Is this normal? Do I  have  to set the flow every time until things
> establish?

Yes and No.  I will explain futher below...

> 3.Is there a way to know how long will my bottle last?

Someone did a calculation for this, but the best way is to weight the
tank and regulator empty, and then full.  You can find the weight of the
CO2 by subtracting, and then periodic weighting will tell you how full
your tank is.  That is the simplest way.

Then Bill wrote in reply:
> Simone,
> I have a manual (beer meister) setup with a 5lb tank. It sounds like you
> have the same situation as I do but over the course of a year I have the
> settings dialed in.
> First, my gauges read as yours do. After the regulator I have to have
> the gauge read 0 or I get to much gas. However if I turn the needle
> valve the gauge does move.

With the needle valve partially closed, here is where you are creating a
little back-pressure and therefore getting a reading on the output side
of the regulator.

> After I set it the bubbles slow down just like yours. So I have to keep
> readjusting the regulator screw over the course of about an hour. In the
> beginning this caused two fish die offs.
> I thought I had the valve set right but when I returned there was gas
> gushing into the tank and all the fish dead. This was due to a large
> temp. change in the tank. It said in a cold MN warehouse, then i bought
> it took it home, hooked it up and set the valves for the cold temp flow
> rate. Well, as the gas warmed it of course expnded and dead fish.

Sorry to hear about the fish Bill.  Did you do this recently, or was
this before you tore-down your tank.  You had some really cool mollies.

> To make a long story short here is what I do:
> 1.I buy the tank at least 24 hours in advance of replacement.
> 2. I let the tank come to room temp before replacing. (24 hrs)

Not a bad idea (both #1 and 2).

> 3. I reduce the pressure after the regulator to 0. This usually  to gets
> me down to 2 or 3 bubble /sec.

This I would have to disagree with.  Proceed on for why.

> 4. Every CO2 tank is different, I have yet to be able to just leave the
> settings from the old tank and hook up a new one. I always have to
> readjust.

You should not have to if you leave it hooked up to the same
fishtank/CO2 reactor. Proceed on for why.

> 5. Readjustments must be done under careful watch and usually over a 1
> hour period. With a new tank I found the settings drift very quickly to
> extremes. The bubbles either fade to a stop or gush!

A very good idea when doing anything like this, though after the initial
setup, re-adjustments should not be necessary.

> 6. After the adjustment period the settings last the contensts of the
> bottle, usually about 3 months.

What size fish tank is it on (I forget what size you have), what size
CO2 cylinder, and at what bubble rate?  I'm just curious here, and have
no opinions.  Obviously the above would determine how long it would

> Hope this helps, I thing your setup is working. If the gauge never moves
> when you turn the regulator screw, first try tapping the gauge. It may
> be stuck.

I guess that could be true.

Okay, so here is why I say that you should not have to adjust your
regulator after the initial setup.  If I am hearing you both correctly
(Simone and Bill), you have no reading (or very little) on the output
side of your regulator.  When I was talking to welding/brew supply about
regulators, they told me that the output guage read not flow, but
back-pressure (I am talking about pressure regulators, as there are flow
regulators that do just that).  If you opened up your regulator with
your needle valve wide open (you definitely want a needle valve, which
goes between your fishtank and the regulator) you would get gushing CO2
with no output reading and very shortly dead fish.

I would suggest that when starting up CO2, you do so into a bottle/glass
of water that has no fish in it.  What needs to occur now is this... 
Start with a fully closed cylinder, regulator, and and fully open needle
valve.  A regulator with an adjustment screw is usually fully closed
when the screw is all the way out.  Open the cylinder slowly, but
eventually all the way to full open.  You should still see no reading on
the output side of the regulator, but pressure on the tank side (usually
up around 900-1100psi).  No gas should be rushing out of the end of the
attached airlline either.  If it is, your regulator is either broken, or
is not fully closed.  With a 900psi or so reading on the cylinder side,
and a 0 reading on the output side (of the regulator, you are ready to

Now you should close the needle valve.  Start adjusting the regulator so
you get around a 4-5psi reading on the output side of the regulator, and
then stop.  Do this slowly, and do not adjust any higher.  Now you can
just crack your needle valve open, and should get a very low flow.  This
will probably be over your one bubble per second rate, but just slowly
adjust the needle valve until you get it.  Once you have the bubbling
rate to one bubble per one/two seconds, you will want to monitor the
tanks pH, and the regulator to make sure both are working okay, and to
make further slight adjustments to CO2 flow (for your proper pH).

Okay, here is the reason I disagree with Bill's assesment.  Pressure
regulators are just that... the regulate back pressure.  By back
pressure I mean the pressure they recieve from the output line (which
would go to your fishtank).  Without giving the regulator any back
pressure, it can't work properly.  When I was looking into regulators
for my setup, I was told that they do best at keeping steady/stable with
a back pressure of at least 3 or 4 psi.  But if you don't have back
pressure to the regulator, the spring in the regulator does not have
much to push against, and can do some adjusting (which would cause
output fluctuations and fishkills).

With your regulator set properly, you could change cylinders without
doing any readjustments.  Once you fully open the new cyclinder, the
regulator will stop with your pre-set 4psi output, and you would have
already set your needle valve to reduce that pressure to your desired
rate of flow.  This would not however change that there would be an
initial surge from the line as you fully open the cylinder and the
regulator gets up to full pressure.  So with that in mind, I would
suggest disconnecting the line from your aquarium before you do the
change of cylinders (but still no readjustments should be necessary).

With all that said, let me add one more suggestion that I learned from a
fellow fish club member.  After the whole cylinder setup has been
running for 24 hrs or so, give the connections another twist (tighter). 
As the CO2 goes through the parts, it makes everything cold, and so they
shrink ever so slightly.  Adding an extra twist after everything has
cooled down (due to the CO2) ensures a nice gas-tight fit between the
parts (cylinder, regulator, needlevalve).

Actually, I have yet another suggestion.  If you want to do CO2 on
multiple tanks, you can put a hose barb directly on the output of the
regulator.  From there you can run airline to a "T" and split it off to
multiple tanks.  Before each tank, you can add and in-line needle
valve.  Airline tubing can at least hold up to 7psi, so you should not
have any problems if you set your regulator to the suggested 4-5psi. 
With this sort of setup, again, you could have multiple aquariums
supplied by one CO2 cylinder (each having their own needle valve). 
Adding another tank to a system like this is a snap.  None of the
existing tanks will/should need to be readjusted.  Just cut the line
before a needle valve (between the needle valve and the regulator) and
put in another "T".  On the new line to the new aquarium, add another
inline needle valve and adjust if from a fully closed position.


pearlsco at u_washington.edu
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