CO2 Tank or Spunding Valve Calibration?

[BrewBlender]

I bought a new tank and hooked it up to my corny keg and checked the pressure with a spunding valve I also purchased. It seems that even though I put 30# of pressure in the corny keg (to seal and test for leaks), the spunding valve is showing 22-24# and staying on that.

I did a soap test and everything seems fine, but the pressure reading is
showing two different readings???

Do I need to calibrate anything on the tank (regulator) or the Spunding Valve? And if so, how do I do that?

Thanks for any advice.
BrewBlender

[Push Eject]

With the hopes that others with more knowledge will chime in here, I'm going to throw out that in my own experience no pressure gauge is perfectly accurate at the low pressures we use in brewing.

Although the differences you are showing seem pretty extreme.

Doc? Jamil?

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[DannyW]

How full is the keg you are testing? If the headspace is very small (keg is very full) then I could see large differences just from the gas lost when disconnecting the tank and hooking up the spunding valve.

[BrewBlender]

How full is the keg you are testing?

It was prettty full...filled to the rim, but not with brim I'll have to try it again when it's not so full.