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I removed the center screw holding the brew head screen, and cleaned the screen and exposed surface of the brew head. Then I put the brew head screen back in place with the center screw. I am unsure how much to tighten the center screw, as I am concerned that tightening it until the screw stops turning may tighten it too much and block water flowing from the center of the brew head. Can someone please tell me how much I should tighten the brew head screen center screw?

It should be snug; tightening it too much will not stop water from getting through the screen, but having it too loose will allow grounds to get behind the screen and clog it up.