CYA - A Bit Confusing

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K

Kit

Bronze Supporter
Mar 10, 2016
340
Medford, Oregon
I have a covered, in-ground SWCG spa. Today I noticed that the level of FC had dropped from about 5ppm to virtually 0ppm over 4 days. The spa had not been used & the air temperature has been unseasonably hot (97 - 101F) during those days. In addition to increasing the output of the SWCG (through my PentAir control panel), I wanted to be sure that my level of CYA was correct. This is where I became a bit confused. I discovered that the recommended CYA range differed widely among the Pool School, the T-100 test kit & my local pool spa. In an effort to sort through the confusion, I would appreciate any solid recommendations from those of you with far more experience than myself.

Thank you so much.
 
I am sure you’ve seen the FC/CYA chart that is the guiding principle for TFP care. We definitely don’t want to mix pool store advice and TFP because it will cause confusion.
 
Post up a full set of your water chemistry results from your test kit. It is always good to get another set of eyes on it to help.
 
For several years I have relied on the recommended levels from TFP. And, as a result, I have been most pleased with my spa. Part of my question regarding the CYA level has to do with that fact that the spa is covered & thus not directly exposed to the sun. As with an indoor spa, I have assumed that the target level of CYA should be lower than for an outdoor spa. I have been using 40 as a target. Is this reasonable?

Here are the targets I have been using:
FC: 3-5 ppm
pH: 7.4-7.6 ppm
TA: 80 ppm
CH: 300-350 ppm
CYA: 40 ppm
 
Those are very reasonable for your situation. You have a unique set up. So variation from the standard norms TFP publishes is to be expected.
 
The CYA of 40 is fine for your set up.

You have a very unique set up. An Inground Spa of over 2000 gallons that is kept covered all the time. That is very unique. Less than a handful, at most, on this forum. Not a bad thing, just that your conditions are not a typical outdoor pool with +/- 20000 gallons.
 
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