Looks like a check value - used to prevent water backflow.
I’m not sure the metal going into the pool is an issue - but if it’s broken should be replaced. These things can rust over time.
Just remove the guts from it. Not needed.
Thank you for identifying this part. Silly question, but how can I tell if it's broken?
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Can you please elaborate on why it is not needed?
In the days of tablet chlorinators, a check valve was placed before them as the acidic, highly chlorinated water could backflow to the other equipment when the pump turned off.
With a SWCG, you do not have acidic, highly chlorinated water in it. So if it backflows, it does not matter.