When is FC too high to go in the pool?

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M

mdublu

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Oct 4, 2007
12
Indianapolis, IN
We just had our pool built last fall and used it for just two months. The builder opened it for us a week ago and shocked it. The FC is 14ppm and CC 0. My kids have been bugging me to go in even though it has been pretty cool here in Indianapolis.

I have searched the internet and this forum but have been unable to find an answer to my question about when is FC low enough for us to swim. It has been cool here and we have been away during the day so I have not had much chance to leave the pool open to release more chlorine.

Thanks for all the information here. I plan on using the chlorine pucks the pool builder has given to me until I don't want my CYA to go up any further and then switching to bleach--CYA is at 30 right now. I also started adding acid last year because my TA was well over 200. It is now down to 180 and I'll keep working on that. I have not even tested PH yet because FC is so high. I have a vinyl liner pool.

Mark
 
With CYA of 30, as sunny as it is today you ought to lose a good bit. I'd probably swim at that level, but in an old bathing suit.
 
14 ppm FC with 30 ppm CYA is technically equivalent to 0.8 ppm FC with no CYA so not that different than many indoor swimming pools. As John says, take an old swim suit, but you should be fine (and don't drink the water in volume -- not that you would). Even if you were off on the CYA test and it was really 20 ppm, that's still equivalent to around 1.8 ppm FC with no CYA so not a problem.

Remember that the secret for lowering the TA is aeration while having the pool at a lower pH. If you lower the pH somewhat, you can have your kids splash in the pool for aeration (but with them in the pool I wouldn't lower the pH too much -- not lower than 7.2).

Richard
 
As a general rule of thumb ( based on what many state health departments consider safe for commercial pools and spas), anything under 10 ppm with normal CYA levels should cause no problems at all.
 
I am wondering about the CYA/Chlorine relationship.

With higher level of CYA, the effective free chlorine becomes lower or less effective but its more stable. Understood that.
We know that chlorine is an oxidizer and sanitizer, so in high concentration is not good.

Now..... assuming I have a free chlorine level that is 20ppm but has high CYA level that makes it equivalent to 3.0 FC (assumed ). In real life scenario if I swim in my pool, will the effect to me as a person is the same as having a 3.0PPM FC or the 30PPM FC ? The abundant power of 20PPM free chlorine to oxidize is there.... right, its just the CYA "hugging" it down. Hugging is not neutralizing right ? Man.... this chemistry is so magical for me....:roll:


Thanks
SPP
 
The FC combines with the CYA to form chlorinated isocyanurates. Think of them as a very special kind of combined chlorine, which they are. They do not have the sanitizing power or oxidizng power of hypochlorous acid, our normal FC.
The more CYA in the water the more that can combine with the added chlorine to form chlorinated isocyanurates.
This is why you need higher FC levels when the CYA levels are high.
The interesting thing about chlorinated isocyanurates is that they test as FC on DPD and FAS-DPD testing.
 
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