Pool is green, readings are off, need guidance.

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G

gustafson

0
Jul 20, 2015
89
Houston, TX
TL;DR: Pool green on return from vacay, managed to get FC very high by mistake, CYA very low, what to do?

So I returned from a 12-day vacay to a green pool. Prior to leaving, I cleaned and brushed the pool, emptied out the skimmers and the pool vac bag, and raised FC to shock levels (24ppm for my 30kgal pool, stupidly assuming CYA was 60 as it has been for months). 7-days in, wifey called me and said the pool looked blue, but the pump was noisier than usual. I suspected the water level had dropped below the skimmers (she wasn't sure about that) and figured that some rain that was expected would address the noise issue.

Fast forward a few days, and as I'm arriving into town, I get a text that the pool turned green a couple of days before. When I arrived home, I noticed the pool was green but relatively clear (you could see the bottom). There were a lot of leaves at the bottom of the pool, and the pool vacuum quick disconnect had come loose. I assumed these two observations were the source of the problem and set to work.

- I first emptied the skimmer baskets which were chock full, scooped up leaves from the bottom of the pool, and noticed the pump was noisy and the filter pressure drop was well under 10psi (vs. the usual 15).
- I thought I'd check the pump strainer basket, and lo and behold, there was the source of the noise my wife had heard. I cleaned and reassembled the strainer basket, and pressure was back up to 15psi.
- I then (stupidly) assumed FC was zero and added 8gal of 10% liquid chlorine to bring FC to 24 (stupidly assuming CYA was at 60).
- After 6hrs, I replaced the quick disconnect on the pool vac (the old one had gone crumbly, presumably due to high FC) and let the pool vac run.
- At this time, I thought I'd test the pool to see if I needed to add more chlorine before going to bed. To my surprise, FC was 35ppm!!! I then tested CYA which appeared to be 20ppm or lower, which is the lowest I've ever seen. That sort of explained the high FC - perhaps FC was not quite 0 despite the pool being green. CH came back at 225ppm, and TA was 90ppm (TA test didn't turn red from green but rather yellow from blue, confirming high FC - a first for me).

Thanks for reading the above. Now for my questions:

- Should I intervene to lower the FC to 10ppm or is it OK let it drift down naturally?
- Should I bother to raise CYA to 30-40, or leave it at 20 or whatever lower number it's at?
- Should I worry about raising CH to 250?
- Does the cooler winter weather (I'm in Houston TX) have anything to do with the above observations, or is it irrelevant?

Thanks in advance for your responses!



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Ok,

Low Cya, does not have a bearing on what your FC will be, only what it SHOULD be. It has no effect on changing the level itself. Also, the high FC did not crumble your quick connect, it was done for already from sun rot/age...whatever.

When your wife said it turned Blue, does that mean just back to the normal color of the pool? Let us know, but for now, don't change any levels. If this is Algae, you'll simply want to carry out the full SLAM until you are clear again. Review the SLAM procedure, and the ABCs of pool chemistry. Follow SLAM to the letter. If you think you were pretty close to the specified ranges for pH before all this, it is likely ok where it is. If you are completely unsure, let the FC drift to 10 or less, and adjust it according to SLAM procedures.

Colder water slows reaction time on some of the tests, but right now your main concern will be FC and it isn't so bad. Lastly, please lay out your test readings as per I've done below so that we can more quickly address the readings to help you.

FC
CC
pH
Cya
TA
CH
CH
 
Thanks @kimkats, @Patrick_B.

Below are the readings as of this morning (along with annotations of last nights reading). Pool looks crystal clear by the way, so the super shock seems to have slayed the algae. I was also surprised why my CH and TA readings are so different this morning compared to last night although I didn't change anything in between.

The pool is obviously way out of balance though so your tips on bringing it back would be appreciated. My instinct is to add water to lower CH to an acceptable level, then add muriatic to lower the pH to 7.5 or so, and continue to SLAM until OCLT checks out OK. Let me know if I should do anything different.

On a side note, I replaced the quick disconnect on the vacuum side, but not the fitting on the pool wall side. The kit came with two washers, one red and one blue. Any idea how I should use those?



Patrick_B said:
FC: 40ppm (measured 35ppm last night?!)
CC: 1ppm (was 0 last night)
pH: 8.2 (or higher)
Cya: 20 (or lower) (same as last night)
TA: 50 (measured 90 last night)
CH: 575 (measured 225 last night)
Click to expand...




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gustafson said:
Thanks @kimkats, @Patrick_B.

FC: 40ppm (measured 35ppm last night?!)
CC: 1ppm (was 0 last night)
pH: 8.2 (or higher)
Cya: 20 (or lower) (same as last night)
TA: 50 (measured 90 last night)
CH: 575 (measured 225 last night)
Click to expand...

I don't have the full solution for you, but here are my thoughts:

Stop testing pH/TA for time being, as you can't get an accurate pH reading with water above 10FC. In fact, it may also be throwing the CH test off, so I wouldn't immediately freak out over that. I wouldn't add water to lower CH at this point...that doesn't lower CH, only dilute it unless you're draining water too since the calcium will still be there. In fact, depending on your supply, it could potentially add calcium to the water. You've got a couple of options to lower the FC...

1)you could let it sit and work itself down over time
2)apply chemicals to lower it (I believe Chem Geek has mentioned that hydrogen peroxide can lower FC quickly and easily)

I would do neither until you have met the requirements of a successful SLAM, then you could do either in my opinion.
 
what azgirl said is the first thing I noticed. You mentioned you tested CYA just before bed so, Im assuming it was dark.

You should be outside in natural light to get an accurate CYA reading. Also, the water temp can effect the CYA test accuracy. Its best to test it at room temp.

grab a sample and bring it inside for a couple hours. Then go outside in daylight and test it again.
 

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I think you should check your FC and CYA tomorrow and get to know your pool brush very well n scrub that nasty green pool down. :mrgreen:

I may have exaggerated nasty but it sounded good. The walls need a good brushing so you may as well do the whole pool. :goodjob:
 
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