Help please

[jurmanji]

Hey.

due to chlorine consumption I assumed I had algae (hard to tell as I have a black-bottomed spa).

it's an 1100 gallon spa with vanishing edge and overflow basin (300 gallon).

current measurements are

CYA 40
shock FC 16
Combined 1.0
All other levels are balanced
I'm losing 9 FC overnight even though the water is sparkling clear. Any thoughts on what's going on?

thanks

 

[Husky25]

Your CC is over 0.5 and if you are losing 9ppm FC, you definitely have something going on. If it were a pool, I'd say brush the walls and SLAM it. However I think there are different guidelines for spas. In terms of SLAM levels, maintaining 16ppm FC only takes between 2-3 cups, depending on strength of your chlorinating liquid.

 

[fajitas21]

I had clear water but was losing a bunch of FC each day, just like you were. Happened just this week.

You mention all other levels are balanced, so I'll assume the pH is not over 7.8 ish. I say that because this week my pool had no FC in it, added more than enough, next day, same problem. My pH was 8.2, high pH reduces effectiveness of FC. I thought I had algae, but correcting pH back to 7.2 - 7.4 allowed my FC to hold.

I will agree with above poster, 1.0CC means that chlorine is chewing on something...

Are your results derived from one of the test kits we use here? Those results can be trusted, strips not so much. Pool store testing is sometimes good, sometimes not. I basically just trust my kit to get me the info I need.

 

[jurmanji]

I had clear water but was losing a bunch of FC each day, just like you were. Happened just this week.

You mention all other levels are balanced, so I'll assume the pH is not over 7.8 ish. I say that because this week my pool had no FC in it, added more than enough, next day, same problem. My pH was 8.2, high pH reduces effectiveness of FC. I thought I had algae, but correcting pH back to 7.2 - 7.4 allowed my FC to hold.

I will agree with above poster, 1.0CC means that chlorine is chewing on something...

Are your results derived from one of the test kits we use here? Those results can be trusted, strips not so much. Pool store testing is sometimes good, sometimes not. I basically just trust my kit to get me the info I need.

Yup. I'm using the taylor kit. PH was 7.1-7.2 when I started slamming last sunday.