I'm not sure I understand the question. Do you mean that the gauge is showing 21 psi after backwashing and adding new, and that it is an increase over what it has always been before? If yes, then it's probably time for a new gauge. Anytime they get wet and then freeze, they go bad. If you removed it during winterization and it got dropped or banged around, that could have done it too. Because my pump stays in operation 12 months out of the year, I generally lose a new gauge each season--but they don't cost that much to replace.
Janet
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