CYA in indoor spa?

[Fungi]

I was told by the installer to add 30ppm CYA for my hot tub. It is in a screened room and never sees any sunlight. Is there any other reason they would recommend using CYA in my spa?

I have very hard water, when changing the water I fill with soft water till 80% full and switch to well water. I was late on the changeover and my CH is only 30. Should I add calcium?

FCL=4.5
CC=.5
TA=120
CH=30
PH=7.8

Thanks!

 

[Isaac-1]

Yes, CYA not only protects chlorine from sunlight, but also buffers its action making it less harsh. You should also boost the CYA level every month as it does slowly breakdown with time, this process goes faster in the warm water of a spa (on the order of 5% per month at spa temperatures)