How much air pressure to put in a well tank

How much air pressure to put in a well tank?
I am installing a used tank to replace the bladderless tank, but have no clue how much air to put in the tank. I recall it's determined by the amount of pressure the switch is set for. Mine is 30 ON, 50 OFF. Can anyone help.
Thanks
Mark
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On Mon, 24 Oct 2005 19:15:06 -0500, snipped-for-privacy@UNLISTED.com wrote:

About 2 lbs below cut-in pressure, so 28 lbs. Make sure the tank is drained and that the drain is open (to the air) when you are pressurizing it.
HTH,
Paul
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