Chlorine too high - SWG, indoor pool

[Jon123]

Hey all (and I suppose I should at least try to page @chem geek )

20k gal SWG, indoor pool.

My last test results (TF-100):
FC 12.5
CC 0.5
pH 7.2
TA 200
CH 300
CYA 65
SALT 3600
TEMP 79F

With that out of the way, the FC had shot up from 5.0 to 12.5 after a few weeks of not being used, but with the pump/SWG running at may 10-20% for about 5 hours a day.
After reading some posts, it sounds like this level of chlorine isn't a safety issue, but I'd still rather get everything in the right ranges.

Looking at the Pool School Chlorine/CYA chart, just sticking with my current CYA at 65, my target FC should be about 4.5.
It's an indoor pool though too, and below the chart it says:

For indoor pools we recommend CYA between 20 and 30ppm.
The reasoning for using CYA indoors is quite different. For more information please ask on the forum.

So, now I'm asking

As-is, I suppose my goal for next year would be to bring CYA down to ~25, and my target FC would be 2.5-4 or so?

Thanks!
Jon

 

[Flying Tivo]

Indoor pools are better of with 30CYA so it serves as a buffer to FC and not be harsh on the skin. 30 is the lowest the kit will measure. Target 5ppm FC so you have some wiggle room.

 

[ajw22]

An indoor pool can benefit from some CYA to buffer he chlorine but doesn't need as much as an outdoor pool. Having CYA of 70 and a FC target of 5 does not create any problems.

I would not dump water to bring down your CYA. It will degrade slowly over time. As your CYA comes down you can lower your Fc target.

 

[Jon123]

@Flying Tivo, @ajw22 Great feedback, thanks! I was going to wait until next years opening (although an indoor pool - it's enclosure isn't ideal for winter), then as CYA drops I'll let it settle in around 30 and target 5 FC.

When does CC become an issue?
My CC is currently at around 0.5 (the lowest the kit seems to register). It's likely less than 0.5, I just get a very faint pink color when testing CC.

I saw in the ABCs of Pool Water Chemistry this:

If CC is above 0.5ppm, you should SLAM your pool. CC indicates that there is something in the water that the FC is in the process of breaking down. In an outdoor pool, CC will normally stay at or near zero as long as you maintain an appropriate FC level and the pool gets some direct sunlight.

I would think an indoor pool should be seeing the same level of CC as an outdoor pool?

 

[ajw22]

0.5 cc is indications of normal sanitation. It is as good as 0.

 

[Flying Tivo]

CC can accumulate more on an indoor pool than an outdoor. UV rays help break down CC, so inside are less UV rays to destroy CC.

 

[duraleigh]

If that was my pool, I would start reducing CYA with water replacement. CYA seems to remain surprisingly stable in an indoor pool.

No hurry, but I would target a CYA of 20-30 (The TF-100 CYA test goes down to 20 ppm). That would allow you to let your FC drift down to 2-4 ppm.......both those levels are ideal for an indoor pool. TFP teaches that "less" is always better if you stay within the suggested ranges. +1 what Tivo said about the CC's.

 

[Jon123]

Excellent, thanks all for your help!