I live in a hard water area and so have to install a combo care scale
inhibitor once a year. I am a month late but have finally got round to it. I
went to unscrew the top of the inhibitor with a variety of good screwdrivers.
They fit in but the screw won't budge. I think the phosphates have overflow
and jammed it tight. Any ideas for how to unclog it so I can actually unscrew
it to change it?

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