Warning: gross. If you haven’t eaten breakfast yet, don’t look!

[YippeeSkippy]

Trying to push through all these comments regarding ahhsome , But since when did hot tubs use CYA? Hot tub is in a screen room and covered.

Even in an inside setting a small amount of CYA helps buffer the chlorine some folks choose to use.

 

[RDspaguy]

You don't need cya in a covered or indoor spa. But dichlor, a chemical sold as spa chlorinating granules, contains cya, so you have to monitor your levels if using dichlor or risk having issues from high cya.