I'm completely new to this, so I don't know if I'm doing something dumb or my regulator is broken. Here's what I'm doing:

Here's what I'm doing:

  1. I connected this regulator to a 5 lb. CO2 cylinder.
  2. Closed the blue output valve.
  3. Turned the regulator knob all the way down (left, i.e. counter-clockwise, i.e. out, i.e. towards the minus sign).
  4. Opened the valve on the CO2 cylinder.
  5. As expected, at this point the input (high-pressure) guage quickly goes up to about 600 psi.
  6. NOT expected: the output (low-pressure) guage quickly goes up to 50-60 PSI (the upper limit), and the relief valve starts sputtering and releasing CO2 quickly.
  7. Finally, as expected, when I shut off the cylinder, the input pressure slowly drops to zero (and then, if I hold open the relief valve or open the output, so does the output pressure.)

I can't find any configuration of knobs and valves that doesn't result in the output pressure spiking and the relief valve opening. Am I missing something? Is the regulator broken? Something else entirely?

NOTE: If I open the output, and open the regulator a little bit (so it's just releasing CO2 into the room) then the regulator knob does control the flow rate, as expected. Turning the knob to the left reduces the flow to a fairly low rate. If I then block the flow by closing the output valve, the output pressure builds to 60 PSI in about a second and the relief valve opens.

2 Answers 2


It sounds like what you're doing is correct. (And I guess you've tried turning it all the way to the right - clockwise?)

The relief valve can be quite sensitive on some regulators, causing it to fire a little prematurely, so it might have been that, but for the fact that you say the dial jumps to 60 psi.

I would double check that the relief lock isn't engaged - this will cause the relief valve to be open all the time. Try turning the ring fastened at the end of the relief valve.

If you still can't regulate the pressure with the knob, then the regulator isn't living up to it's name! Sounds like you have a broken regulator.

  • Turning the regulator knob clockwise about halfway causes the pressure to spike even faster - the needle jumps almost instantly, whereas it takes almost a second to max out if the regulator knob is all the way counter-clockwise.
    – Josh
    Feb 21, 2013 at 20:36
  • There is a ring on the relief valve - pulling it releases the pressure faster, but turning it doesn't seem to do anything. Anyway, it doesn't seem to be locked open: when I turn off the CO2, the relief valve closes as soon as the gauge drops to 52 PSI, and the pressure stays there unless I hold the relief valve open manually.
    – Josh
    Feb 21, 2013 at 20:43
  • This does sound like it's broken. You should be able to turn down the regulator so the relief valve doesn't fire. The valve is there in case there's some abnormal condition causing overpressure, which shouldn't be the case with a brand new one.
    – mdma
    Feb 21, 2013 at 20:52

CO2 Regulator knobs are counter intuitive for 1st time users. When you "close it" like a faucet clockwise in fact you are adjusting a screw/pushing a pin that allow more CO2 flow. Short: Try twisting all the way counter clockwise. If it still fails, have your reg checked.

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