why NOT keep a high CYA ?

[lenhorn]

My CYA is ~50 and I consume about 2.5 PPM chlorine per day.

Will bringing CYA up to, say 90 (and following Bens Best Guess CYA chart), cause less daily chlorine consumption since its protecting it from being burned out by the sun?

What is the downside to doing this? [ I assume there is, otherwise poolforum wisdom would recommend this higher CYA level ]

Thanks in advance
Len

[chem geek]

This issue is currently under investigation. Some people have reported that they can use higher CYA levels and correspondingly higher FC levels (according to Ben's chart) and come out ahead with lower chlorine loss. Some experiments are being done at the TroubleFreePool.com forum (near the end of this thread) to sort this out. So we don't have a definitive answer yet. If it were easy to reduce CYA in the pool, then I'd just say to try it, but since it's easy to increase CYA but not to decrease it, this isn't a simple test for you to do (the experiment is being done in an attached spa to a pool that has a separate circulation option so changing chemical amounts is easy).

Prior to this investigation, the thought was that lower CYA levels were better since up to half the chlorine was lost in a day somewhat independent of CYA level. What we are finding out is that the protection from CYA does appear to be greater than expected and this is due to additional protection mechanisms not described in some charts the industry used.

Richard

[CarlD]

Usually this issue is addressed as one where the owner got the CYA too high inadvertently. Aylad (Jan) insists she has far few problems keeping her CYA at 80 and running higher FC levels. I have no reason to doubt her since Jan knows her stuff really well, but it's still anecdotal info, not a controlled test testing a mechanism.

There are two drawbacks to running a high CYA (like 100ppm).
First, you MUST have an FAS-DPD chlorine test kit--Leslie's sells them online for about $20 (that's just one test, not the whole kit with pH, T/A, CYA and CH).
Second, you'll need to run higher chlorine levels a la Best Guess Table. Ben suggested that the only thing you should be concerned with (assuming a healthy pool) is fading bathing suits--he suggests "Last Year's suit", not you expensive, fancy new one.

[lenhorn]

thanks for the replies.

the issue of "fading bathing suits" is part of my confusion concerning CYA and chlorine. if the CYA causes the chlorine to be less effective against pool nasties, then shouldn't it be equally less effective fading bathing suits ?

since its still able to fade bathing suits i wonder if there are health risks at these higher levels of chlorine ...

thanks
len

[aylad]

thanks for the replies.

the issue of "fading bathing suits" is part of my confusion concerning CYA and chlorine. if the CYA causes the chlorine to be less effective against pool nasties, then shouldn't it be equally less effective fading bathing suits ?

since its still able to fade bathing suits i wonder if there are health risks at these higher levels of chlorine ...

thanks
len

I am the one that runs the high CYA levels--I keep it at 80-90......and we don't have problems with faded suits...at least, not so far in 5 seasons.

Janet

[lenhorn]

hit janet.
i looked for your results in the bleach usage survey, but didn't find them.
how much chlorine do you lose / day ?
did you ever keep a lower level of CYA and find that you lost more chlorine ?

thanks
len

[chem geek]

As for the fading bathing suits, since the disinfecting chlorine level is the same in a high CYA high FC pool as in a low CYA low FC pool (using Ben's chart), the rate of fading or destruction of elastic rubber in swimsuits should be the same while in the pool. The problem is when one gets out of the pool, then the total chlorine "reserve" available (which is the FC independent of CYA) can over time be more harmful for swimsuits. A quick rinse in a fresh water shower or soaking the swimsuits in fresh water should help.

My wife's experiences with her swimsuits getting ruined after each and every winter of use in a commercial indoor pool with no CYA and typical 2-3 ppm FC (I finally measured this) while having absolutely no problems when using our own pool during the summer with 20-30 ppm CYA and 3 ppm FC tells me that the higher CYA and FC combination will probably not result in any noticeable difference in swimsuit degradation.

Richard

[leejp]

I had been consumin 2~3PPM/day which was a about a jug or jug and 1/2 of 96oz 6% bleach/day. Bleach works great but buying/lugging ~10 jugs of bleach/week is definately not very convenient.

Think I'll boost my CYA to ~90-100 PPM and keep my FC ~7~8PPM. I lose enough water through splashout/overflow/backwashing so that I'm not too worried about CYA build up. If there's little downside to high CYA, why not?

Here's an informal bleach usage survey I ran last year...