Small pool, Chlorine level is driving me nuts.

I am a new pool owner, purchased a short-sale home, so I got ZERO info from previous owner.
The pool is an excercise pool with built in Badu swim jets, approx 4200 gallons. I cannot seem to get the chlorine right, and it has not a "Bad" smell, but it doesnt have that nice clean chlorine smell either. Others have told me the pool smells "different" from most pools they swim in.

I use the LaMotte 2056 ColorQ Pro 7 Digital Pool Water Test Kit which seems to be accurate.

I use Calcium Hypochlorite granules for sanitizing, Sodium Persulfate for shocking and Cyanuric acid for Sablizer.

Latest test results:
FCL: .18
Total CL: .36
pH: 7.5
ALK: 134
HRD: 314
CYA: 71

Here is the problem: My pool chem app advises me to add CL, but when I do, the next test always says "Combined chlorine concentration is above recommended levels. add Monopersulfate" which I do, which seems to drop the CL again, and the cycle repeats when I add more CL.
Ive never seen my Free CL level above .4 (POINT 4) and I think it should be around 3 or 4 correct?
Any suggestions?

More info. Inground INDOOR pool, not sure what the liner is made of, seems fiberglass like. Circ pump on about 6 hours a day. the pool is not used much, only about 1 hour a day, and we keep it heated to 85 degrees.

+ Do NOT use sodium persulfate (I hope you mean monopersulfate); it's a waste or worse.

+ You have WAY too much CYA for an indoor pool. Normal recommendation is ZERO. 10 ppm *might* help you avoid some of the more noxious disinfection by-products, but again, 10 ppm is the max.

+ Drop the "app" -- almost all of them are written by people who know NOTHING about pool chemistry. I've got a guy in the pool biz section now, who's written an app . . . and is asking if salt will dissolve on the bottom of a pool!!! The only way to find out if it's reliable is to validate it yourself -- but by the time you can do that, you won't need it!

+ Test strips are generally in-accurate. We haven't compared the LaMotte with any standards, but . . . test strips are generally inaccurate.

+ 1 hour per day in 4200 gallons IS a lot . . . if you are swimming and sweating. People goo is the primary contaminant source on indoor pools, and an hour of sweat (85 degrees) in 4200 gallons is a lot.

+ Read the Best Guess page linked in my sig, to get a handle on the CYA / Chlorine relationship. Your levels are WAY too low for a pool with that much stabilizer -- it's not close to sanitary.

Thanks for the tips. I did mean NaPersulfate, not Monopersulfate. I thought they were the same thing.
I also thought that i needed some level of stabelizer (cya) in the pool. But you feel that zero is ok for a small indoor pool?
How do i lower the CYA level? or will it go away on its own if a stop adding any more?
My Lamotte tester is a Photometer, uses test tubes inserted into the machine, so I think its accurate. (was expensive!)
I will study your best guess link and let you know if I have any more questions.

Also, should i be using nonstablized Chlorine? or stick with my Calcium Hypochlorite granules? (I dont know if my granules are stablized or not)
What is the best way to get nonstabilized Chlorine? Is that just plain Walmart Bleach?

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Originally Posted by Greenfrog

Thanks for the tips. I did mean NaPersulfate, not Monopersulfate.

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From Wiki:

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"Sodium persulfate (Na2S2O8) is a chemical compound. It is a strong oxidizer. It is a severe irritant of the skin, eyes, and respiratory system."

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Potassium monopersulfate is mostly worthless, but it doesn't do much harm except to your wallet. Sodium persulfate can be a serious problem. I'm surprised the results haven't been worse.

Regarding your tester, Lamotte isn't a total junk company, but expensive is not well correlated with effective or accurate, and like I said, we haven't validated them.

Calcium hypochlorite = cal hypo IS unstabilized. But, check your label. If it doesn't say 68% (or higher) available chlorine, it's yet another mystery blend.

Given your history, I'd drain and refill. If you want to add 10 ppm CYA, OK. But no more than that. If you want to use your cal hypo AND it's unblended, that's OK too. But you have to verify it. You really shouldn't be using anything regularly except an unstabilized chlorine source (bleach or cal hypo), borax (to raise the pH) and sodium bisulfate (the sulfuric half-acid). Muriatic would be preferred if you were outdoors.

Ok ive now completely drained my pool, and started from scratch with some 6% bleach and some Sodium Bicarbonate to adjust the ALK. Here are my new readings. Should i keep adding bleach slowly, or do I need to "shock" the pool to get the FC up to 3?

FC: 1.36
TC: 1.57
pH: 7.4
Alk: 130
Cya: 7

Don't mess with bicarb. Just use bleach to chlorinate; muriatic acid or bisulfate to LOWER pH and borax to RAISE it.

Do NOT add any more CYA. Do not worry about calcium UNLESS it is high.

Dose with bleach to 3 ppm before use; Dose to bleach to 3 ppm AFTER use. You'll have to experiment with doses. Start with doses of approximately 1 quart of PLAIN 6% bleach, and see where that puts you.

Thanks so much, your help has been invaluable!

A quart of 6% bleach should add between 3-4 ppm of chlorine to your pool, so, a cup should add approximately 1ppm.

Well, I have drained my pool and started over. Its been 3 weeks or so and I still have concerns over my CL level.
I seem to have high Total CL, and very low Free CL. I use 6% walmart bleach to chlorinate.
Latest readings:

Free CL: .12
TotalCL: 2.95
pH: 7.5
ALk: 157
Cya: 8

Should I be concerned about the difference between Free and Total CL levels?