So, here's an example situation. I have a pool that is correctly balanced, and an FC level of 4. I add an ounce of bather waste. The chlorine goes to work and oxidizes this waste and kills bacteria. Would there ever be any CC in this process, because there was enough FC to do the job? Would it be correct to say that if my CC is above 0.5, then my FC is used up? If this happens, I slam the pool, or shock it, to stay on top of the waste..
First, there are others that can explain this better but I'll try. You
could (for example) start with an FC of 4, add bather waste, then measure FC of 2.5, CC of 1 (TC was 4=4+0 but now TC is 3.5=2.5+1.0 and some chlorine is simply gone away). The CC is an intermediate step, chlorine in the process of being used up. Not useful in this form, actually a sort of waste product, gives the pool that "chlorine smell".
That CC will go away eventually, probably using up some of that remaining FC as it does and depending on things like sunlight and wind, for example.
In this example, if you tested and measured FC down to 2.5 and CC of 1.0 you would certainly increase FC back to 4 or to the top of the recommended range for your CYA level, maybe a touch more, and you'd probably be sure to not cover the spa so that CC's might benefit from air circulation to help them disperse. If, say tomorrow, you still saw CC's high, you might slam the spa but really, it's probably get back to a normal 0 to 0.5 ppm CC pretty fast as long as you were keeping the FC up. If you let the FC go to zero, then that is a different issue for the CC's will have a harder time going away and FC of zero is never good for keeping things sanitary.
Now, if the spa got nasty for some reason. Say you found a dead critter in the water, really ugly. Probably you'd dump water and start over but if you chose to not do that you'd shock or slam the spa. You'd find FC low or at zero, raise it up to shock/SLAM level, and the CCs would get raised or even really high as the crud was being burned up by the chlorine. CCs drift lower as all the crud is sanitized.
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So, here's an example situation. I have a pool that is correctly balanced, and an FC level of 4. I add an ounce of bather waste. The chlorine goes to work and oxidizes this waste and kills bacteria. Would there ever be any CC in this process, because there was enough FC to do the job? Would it be correct to say that if my CC is above 0.5, then my FC is used up? If this happens, I slam the pool, or shock it, to stay on top of the waste..
First, there are others that can explain this better but I'll try. You
could (for example) start with an FC of 4, add bather waste, then measure FC of 2.5, CC of 1 (and some chlorine is simply gone away). The CC is an intermediate step, chlorine in the process of being used up. Not useful in this form, actually a sort of waste product.
That CC will go away eventually, probably using up some of that remaining FC as it does and depending on things like sunlight and wind, for example.
In this example, if you tested and measured FC down to 2.5 and CC of 1.0 you would certainly increase FC back to 4 or to the top of the recommended range for your CYA level, maybe a touch more, and you'd probably be sure to not cover the spa so that CC's might benefit from air circulation to help them disperse. If, say tomorrow, you still saw CC's high, you might slam the spa but really, it's probably get back to a normal 0 to 0.5 ppm CC pretty fast as long as you were keeping the FC up. If you let the FC go to zero, then that is a different issue for the CC's will have a harder time going away and FC of zero is never good for keeping things sanitary.
Now, if the spa got nasty for some reason. Say you found a dead critter in the water, really ugly. Probably you'd dump water and start over but if you chose to not do that you'd shock or slam the spa. You'd find FC low or at zero, raise it up to shock/SLAM level, and the CCs would get raised or even really high as the crud was being burned up by the chlorine. CCs drift lower as all the crud is sanitized.