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Today I think I finally figured out why the Milwaukee regulator behaves as it does. When I first set up the newly filled tank of CO2, I set the regulator to about 20 psi, set the bubble rate, and come back to look at it after a half hour or so - the regulator is putting out just above zero pressure. So, I tighten the knob some more to get back to 20 psi, come back in a half hour and the regulator is back to near zero. After a day of this, the second day the regulator stays where I set it and the bubble rate is therefore constant.

Then, as the liquid CO2 runs out, the bubble rate goes up a great deal. I loosen the knob until the bubble rate is back where I want it. But, it is soon back too high.

Both of these quirks can be explained if you accept that that regulator, at any given tightness of the adjustment knob, produces a pressure that is highest when the tank pressure is lowest, and lowest when the tank pressure is highest.

A newly filled tank is very cold, and stays that way for hours. So, the tank pressure is around 500 or so psi, not 700 as it "should" be. That low tank pressure means the output pressure is high. As the tank CO2 warms up, the pressure in the tank increases, and the output pressure drops. When it finally reaches room temperature the tank pressure is about 700 psi, and the output pressure stays at whatever it is set at.

But, when the liquid CO2 is used up, the tank pressure begins to drop. That means the output pressure rises, increasing the bubble rate. This rising of the output pressure continues until the tank is empty. This is the cause of "end of tank dump".

There is only one "solution" to this: let the newly filled CO2 tank sit until it warms up to room temperature, before connecting it to the regulator. Then, as soon as you see the tank pressure start to drop, disconnect the regulator and get a refill of CO2. I just live with the problem, knowing I have to readjust the output pressure every half hour for a few hours after I hook up the newly filled tank. And, I start backing off on the adjustment knob as soon as I notice that the tank pressure has dropped from 700 psi.
 

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so does the milwaukee eliminate the need to make those initial adjustments?
You need to readjust the regulator every time you refill the CO2 tank. When you refill it, you remove the regulator assembly from the tank, and to do that, first you back off the adjustment knob until it is loose. Then you close the valve on the tank and remove the regulator. When you have the tank filled and are ready to install the regulator again, first you screw the regulator onto the tank, then, making sure the adjustment knob is backed all the way off, you open the tank valve. Now, you tighten the adjustment knob until you get about 20 psi on the output gage. If you didn't touch the needle valve before you removed the regulator you should be back at the bubble rate you want.

But, until the tank of CO2 warms up to room temperature you have to keep tightening the adjustment knob every half hour or so to get the pressure back up to about 20 psi. This is a very cheap regulator, that is only good for maintaining a constant output pressure if the input pressure is also constant. Good regulators will hold the same output pressure for any inlet pressure. But, good regulators cost a lot more too.
 

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I work a lot with air conditioning and nitrous. Generally when you compress a gas is gets hotter and when it is released the temp drops, is co2 the opposite of this?
 

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CO2 is a unique gas because its state depends on pressure and temperature. At room temperature it will be a liquid at about 700 psi or above. At normal atmospheric pressure, it will be a gas unless it is at minus 80F, or something near that, where it is a solid, and it cannot be a liquid at all. Also, it takes considerable heat energy to change from a solid to a gas, or from a liquid to a gas. But, it takes less energy to change from a liquid to a solid. CO2 in a pressurized tank, as we buy it, is a liquid, with extra space for some CO2 gas to exist, which fixes the pressure at around 700 psi at normal room temperature. But, when you refill the tank, the liquid CO2 that is put in the tank has to partly evaporate - change to gas - to fill the extra space, and that means it absorbs a lot of heat doing that, which chills the tank and the liquid CO2 down near water ice temperature, if not colder. So, the tank and its contents stays very cold for quite a long time after you get it. All of these characteristics make CO2 useful for a lot of different things.
 

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All I've done to fix the dropping pressure problem on this regulator is to use a working pressure of 40 psi instead of 20 psi. It's been running like this for about 7 months now without any problems.
Once the tank warms up it will run at any pressure until it runs out of CO2, in my experience.
 

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Once the tank warms up it will run at any pressure until it runs out of CO2, in my experience.
So the right gauge can be any psi after "acclimation" and it will be fine? I have had the tank up and running for a couple weeks now and there are still fluctuations in the psi.
 

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The needle valve seems to work best at over 15 psi, in my experience, and I doubt that you would want more than 40 psi for any reason. Other than that, as long as you can adjust the bubble rate with the needle valve to whatever value you want, the output pressure is ok.
 

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So glad I swap out CO2 bottle instead of filling them, no acclimation worries, cause the tanks sit for awhile before I ever use them.
 

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I work a lot with air conditioning and nitrous. Generally when you compress a gas is gets hotter and when it is released the temp drops, is co2 the opposite of this?
All gases work the same way, when your compressing gases, like your example, even CO2 gets really warm. But when they fill CO2 cylinders, they are just transferring a liquid, and a little of that liquid CO2 does turn back into gas as its being filled, and that chills the tank.
 
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