How much FC is too much for a vinyl liner?

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Jul 11, 2014
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NJ
What is (if any) threshold where FC could damage your liner? I mean I see Mustard Yellow shock recommendations at like 30 or higher in some cases where CYA is slightly larger.
 
It all depends on CYA levels. In theory you could have a high enough CYA level that 500 ppm of FC would be safe, though I'm not willing to test out that theory. On the opposite end of the spectrum a pool with a true 0 CYA level could suffer some liner damage with just 10 ppm FC.
 
It all depends on CYA levels. In theory you could have a high enough CYA level that 500 ppm of FC would be safe, though I'm not willing to test out that theory. On the opposite end of the spectrum a pool with a true 0 CYA level could suffer some liner damage with just 10 ppm FC.

And by damage, is that staining?
 
Stay within guidelines for your Cya levels, shock or otherwise and you will be fine. Outside those parameters is dangerous for a liner pool in particular.

I've been wondering about this myself....By guidance, do you mean somewhere between recommended level and SLAM level, or is there a recommended, for example, no more than 3ppm over recommended level?
 
Bleaching, liner degradation, generally bad stuff. But to have a true 0 CYA it would have to be a fresh fill that has never had any stabilizer or stabilized chlorine added. Even just the tiniest bit of CYA in the water helps to buffer the effects.

So, out of curiosity, why do you ask?

And 440, water is completely safe to enter anywhere between minimum and SLAM levels. Below that and it might not be sanitary, above that and the chlorine can be increasingly harsh.
 
Bleaching, liner degradation, generally bad stuff. But to have a true 0 CYA it would have to be a fresh fill that has never had any stabilizer or stabilized chlorine added. Even just the tiniest bit of CYA in the water helps to buffer the effects.

So, out of curiosity, why do you ask?

Because I've had it at SLAM levels (maybe a 1-2 ppm over the recommended) for a few days now. I've gone through several gallons of LC (35k pool).

I just want to make sure I'm not hurting my liner (which is only 2 years old).

This morning for instance I was flying blind (the night before it was 17 and I added a gallon so it was 20ppm - then I realized my CYA was 40, so technically that's 4ppm over recommended levels, I have the filter on all day today and the pool has had complete sun, so I assume it will drop each day by 1.5-2ppm (maybe more?)). Again, I just don't want to damage anything.
 
At 40 CYA you have a pretty good buffer. Odds are good that if you go a little over SLAM levels then you won't suffer any problems. The more you go over though, the more you chance problems. There really is no absolute limit to safe levels given all the variables involved. Any time you go above SLAM level there could be problems and the further above you go the more likely that will be. The odds of a problem by occasionally going a few ppm above in a stabilized pool are very, very small.
 

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