I believe I have the same problem listed here - the threads of the receiving side (in other words, in the filter casing itself) are stripped. Did you find a good solution in terms of up-sizing the threads on the gauge and boring a wider hole/threads? Seems risky - but my alternative is a whole new top portion of the filter ($250).
My filter is a Pentair CCP320, not a Hayward, but I'm guessing the same idea at play.
My filter is a Pentair CCP320, not a Hayward, but I'm guessing the same idea at play.