Quote Originally Posted by chem geek View Post
45 ppm CYA is OK. I usually recommend around 30 ppm (initially I recommended around 20 ppm), but you're probably fine up to at least 50 ppm. We started to see possible hot tub itch incidents with longer Dichlor use, but it was hard to determine whether that was at 100 ppm or some other specific level so I've been conservative to just recommend relatively low CYA amounts.

9 ounces of 6% bleach in 450 gallons would be 9.6 ppm FC. If you are using the spa 3.5 times with 3 people for 30 minutes, then that is 5-1/4 person-hours and would normally require 26 ppm FC to oxidize the bather waste. Since you are using substantially less and apparently maintaining a chlorine reading, do you have an ozonator? That would explain why you aren't using as much chlorine with frequent usage. Usually it would cut down required chlorine amounts by about half while in your case it seems to be cutting it down to 1/3rd.
Thanks for the reply chem geek. I think the way I wrote the above was a bit misleading now that I read it again after your response. I use it 3 times a week and sometimes 4. My boys do use it with me but not all the time. If my 5 year old gets in with me, he is only in for about 15 minutes while I am in about 30 minutes. He does get in with me all the time. My 9 year old gets in but not often. I am not 100% sure about the ozonator. I am pretty sure that I do not. After reading your calculations, I believe I am putting more in. I will check it for a week by recording the amount each time and write it down. This way I am not forgetting if I add some and forget that I did. I will say though, I am able to go at least 2 days, sometimes 3 before I have to add any. I do really appreciate the help and I am slowly getting the hang of this. Anything else is greatly appreciated.

Jim