[Bucho]

Are you talking about a CO2 generator? As in baking soda and citric acid? Or are you talking about CO2 over calcium carbonate?

 

[Bucho]

You typically set a regulator to ~20-30psi. This is your working pressure, after it has been stepped down from the high pressure. From this point, you introduce a metering valve into the equation, and you don't really think about the pressure on that side of the business.

The truth is, the "working pressure" isn't all that important, to a large degree. You wouldn't set it to 1 psi, because changes in ambient temperature could negate your pressure, to the point that nothing flows - or the flow would be unstable, and the output inconsistent. I also want to say (if memory serves) that a typical one way (check) valve needs about 2-3 psi to open. On the other hand, if you have more than 30 psi, you may find that a solenoid (of the category that we'd normally use) could have trouble operating against the pressure. So, this is the working pressure range that has been found to be stable in most climates, assuming household climate controls.

 

[Bucho]

You're going to negate that pressure if you have a metering valve, anyway. As I mentioned before, it's more or less just a means of setting a pressure that works with both ambient room temperature fluctuations, and the mechanical limits of a solenoid. (if you have one) So if a lower pressure works in your case, there's no reason not to do so. More refined solutions for more educated users, is always the rule.