What’s this?

[JamesW]

Maybe from the Rainbow check valve before the Rainbow chlorinator 320 feeder or maybe the check valve from the Rainbow 320 chlorine tablet feeder.

Do you have an in-floor cleaning system?

If yes, have any of the cleaning heads popped out?

 

[JamesW]

I would remove the tab feeder and the check valve before the feeder.

 

[JamesW]

There are probably other parts of the same thing so keep a lookout for the other parts that go with this part.

 

[Lilypad]

Maybe a flow gauge for a pool cleaner?

 

[Mikecn]

Am I understanding correctly that you found that on the deck and not in the pool itself?

Is it possible that it didn’t come from the pool at all?

I find things in and around my pool all the time that didn’t come from it.

Do you or your neighbors have a diesel? To me it is remarkably similar to the check valve on a 1/2 gallon adblue refill bottle. They use a stainless steel spring as well as adblue is urea and corrosive.