Cl Loss Seems Excessive

[y_not]

As you all know, I'm a TFP veteran. I have this thing down, even bringing friends on board.

This being my 3rd season on BBB, I'm seeing some unusually high FC loss this July.
Temps have consistently been between about 98-103F with our usual blazing, baking sun.

I have had to go from 30ppm CYA, to 40ppm CYA, to 50ppm CYA, because I'm dangerously close to, or right at FC minimum each evening after dark with the lower CYA levels.
I normally keep her at 40ppm CYA, but I had a pump leak and lost maybe 1/4 of my water, so had to raise it after I filled it back up. But I waited a while till the weather warmed before I bumped it up to 40ppm CYA.

I was gone on vacation for less than a week, so I left my family to tend to it. They're pretty well trained in TFP ways, but it got down to 1.5ppm FC @ 30ppm CYA when the heat really hit. So I brought her up to shock levels and did an OCLT, passing just fine. Only 0.5ppm FC loss and 0.5ppm CC.
Nothing living in there.

I'm now at 50ppm CYA and staying above the minimum, with more room to spare now @ 1-2ppm above the 4ppm minimum each evening, dosing each night to 8ppm FC. I was feeling pretty confident I hit a CYA level to match our blazing, high elevation sun. A 25% to 38% loss seems about right, with a daily bather.

But this last Monday night after sundown, I dosed it to 9ppm FC for more head room. As the heat is kicking up a notch, and my niece is here swimming like a fish for several hours per day.

Tonight I tested and was right at the minimum of 4ppm FC. WHAT?? :screwy: A 56% loss?
She swam less today, Tuesday, than she did Monday, and I had far more FC loss.
Not really any hotter than the day before, and my niece was only in the pool about 2 hrs, with 45min of that having one other bather In addition. So what, 0.2ppm FC loss per bather, per hour, right? So we can say about 0.6ppm of that was from bather load, yeah?

Any ideas?

Water is clear... after the filter runs all night. Not as sparkly as before my niece got here, but that's because my Intex filter is so horrible!!
*rectifying that this week.

I do have a consistent 0.5ppm CC reading, which I didn't have before she got here, like almost never!
She showers daily before she gets in, but uses commercial sunscreen.

Ps. Cl additions have been tested and verified 30min after dosing. My 6% bleach is only about 2 months old, kept in AC at the supplier, new stock brought in every 2 weeks from the manufacturer to their regional warehouse, and runs consistently at 7%, out of the bottle. Verified with both Cl additions, as well as a 10,000:1 dilution testing.

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[ship of fools]

Sounds to me like you may have some organics in there. The consistent CC readings means you are killing something regularly.

When you did the OCLT what were your starting and ending numbers?? From what i have read it is more accurate at SLAM levels.

 

[y_not]

Sounds to me like you may have some organics in there. The consistent CC readings means you are killing something regularly.

The thing is my 11yr old niece is swimming for several hours, daily, every single day since she got here, that's when the CCs started. Once and a while it's 0, but never higher than 0.5ppm CC.

When you did the OCLT what were your starting and ending numbers?? From what i have read it is more accurate at SLAM levels.

I was at 30ppm CYA at that time, so my shock level was 13ppm FC, which I brought up to that after sunset, then verified 30min later at 13ppm. Tested it right at sunrise and got 12.5ppm, only a 0.5ppm loss and well within the 1 drop margin of error of the test's accuracy.


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[JasonLion]

Chlorine loss varies with water temperature, amount of sunlight, and people hours of swimming. Note that amount of sunlight is something that counts intensity as well as time and is very difficult to judge by eye.

With the water quite warm and people swimming and CYA around 50, having only a 56% daily loss is doing really well.

There could be something more going on, but I doubt it.

 

[y_not]

Thanks Jason for the sanity check, it just seemed excessive, as I'm not used to that much loss and was really just wondering if it was out of line or not.

Can my pathetically inefficient Intex filter be leaving too much organic particulate matter in the main body of water, such that it causes a Cl demand?

I ask because the water is pretty cloudy and ugly after my niece swims. I can still see the bottom, and it is by no means green. It does filter out over time though.

I'll have a sand filter up and running by the end of the week though, so I'm anxious to see how that changes things.

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[y_not]

UPDATE:

So today, I only went down to 5ppm FC, 1ppm above min. I'm wondering if dosing to 9ppm FC @ 50ppm CYA, is a bit too high for the nearly all day sun the pool gets, and it's just burning off above what the current CYA can protect against. I'm going to go back down to the previous 8ppm FC that I was dosing to before, as I'm hoping this will actually result in less net loss.