Need help with chlorine levels

[bri12]

Hello,

I have a 17000 gal inground gunite pool.
I've had trouble with greenish cloudy water for awhile now and after advise from several other sources I was getting nowhere. I found your forum and have read alot, and was able to determine I needed a good test kit. Got one. Then was able to determine after testing that my CYA was way too high, and that was why I was getting nowhere. I drained my pool the other day and after refilling, my test results were the following:

FC = .5 or 0
TC = 1
CC = .5
PH = 7.0
TA = 100
CH = 300
CYA = 60

The confusion I'm having is that I determined from you forum that I needed to get my shock level up to around 24 based on these numbers. So I got a good amount of bleach and started adding over the last few days to try and get to 24. I've added a large amount of bleach over a the last day and a half, and the highest it got was 10.5 late yesterday, so I added another 2 182 oz containers, with the intention of testing again last night. Unfortunately, I fell asleep while waiting before I did.

I tested this morning and found the FC back down to .5 I'm now totally confused. My pump is running continuously over the last couple of days. Also ,the water is turning bluish, and is somewhat clearer, but I also have alot of patchy foaming on the surface.
I added 2 more 182 oz a short time ago and plan to retest after about an hour.

Since my initial test results above after refill, I've not tested for anything else besides FC. I'm curious to see if I'm missing something with all the FC loss and the difficulty in getting up to the level I was attempting to with the CYA of 60.

Thank you for your advise and for this forum.

[bri12]

Update, now my FC is 3.5

Water is bluer and clearer, and the sudsy patches are gone for the most part. I am assuming I'm on the right track even though I was never able to get the FC level up to the point suggested by my CYA of 60.

Should I try an keep it at the level it is at now, or move it up? Also, when should I do the other tests again?

Thanks in advance.

[CarlD]

Hi, and welcome to our forum, BRI! Unfortunately, in most of the country pools are closing or closed so our "throughput" lately has been a little slow.

Let's look at your numbers:
FC = .5 or 0 It's .5, which is not going to fight off algae given your CYA level (which I must question--more below). If it was .5 and TC was .5 it'd be better.
TC = 1 TC = FC + CC so, if we have FC and CC, we know TC. If we have FC and TC, we know CC. So let's cover it in CC.
CC = .5 The ideal CC is 0. However, when FC is positive, we frequently have CC indicated of .5 or less. If you re-run the test using 25mg of water rather than 10, each drop equals .2, not .5. Sometimes then, the .5 or less now looks like .2 or less. Otherwise, CC indicates you have metabolized free chlorine--ie there's something you are fighting. Since FC is .5 also, this is clear.
PH = 7.0 Normal pH range is from 7.2-7.8. For vinyl pools, anything below 6.9 is cause for concern. But with gunite, it's no big deal. In fact, I would leave your pH at 7.0 because chlorine is more effective at lower pHs than at higher ones. You can raise pH to more comfortable levels later when your chlorine holds.
TA = 100 Not to worry. For now, it's no issue. In fact, it should never be an issue at 100, but sometimes it is. However, I see no evidence of that. With gunite, though, never let it get past 120-125.
CH = 300 This is right in the middle of the recommended range for hard-sided pools like gunite--200-400 is the recommended range. Don't change it.
CYA = 60 This is where I have a problem. If you just emptied and refilled your pool, how did you get a CYA at this level? It just doesn't make sense because it shouldn't be in your fill water. I can only guess at 3 reasonable possibilities:
1) You need to re-run the test as you ran it incorrectly.
2) You've added CYA by either adding it directly, or by use of Tri-Chlor Tablets or Di-Chlor powder.
3) There was a lot of water left in the pool when you drained and the CYA had been insanely high before, and this is the residue of that.


But let's assume for now the number is OK. We'll go from there. A CYA level of 60 should use a shock level of 20ppm, not 24(?). But to get there, you'll need to use the same method we recommend for fighting algae, as you are fighting SOMETHING that's using all your chlorine.

Each gallon of 6% bleach will add about 3.5ppm of FC to your water. That means 5 3/4 gallons of 6% to get from 0 to 20ppm. (or half that of 12% liquid chlorine "LC"). What you need to do is add that much bleach to get your FC to 20. You'll have to check FC and add bleach/LC 3 times a day until your water holds the chlorine. If you've added it in the morning on a sunny day you WILL lose some to UV breakdown, but it shouldn't drop 15 points. Yeah, it's going to take that much chlorine until you kill whatever it is that's in your water.

If your water isn't clear, you should also vacuum to waste once a day, brush your walls once a day and back wash whenever the pressure rises.

But re-check that CYA test, please.

Good luck!

Carl

[bri12]

Thanks for the reply Carl.

Sorry, I should have clarified with my initial post. My CYA was insanely high, around 120 or so due to previously overuse of tri-chlor tablets and Di-chlor powder. That is why I drained the pool after reading alot in these forums.

Anyway, the pool is clearing up and getting more blue. Should I proceed to try and elevate the FC? Or should I try to maintain at my latest test result of 3.5?

Thanks again.

[CarlD]

If your CYA is 60, you should be able to get your FC to 20 at least temporarily. If not, you are fighting something, I believe.

[Watermom]

A question ----- I'm still not clear on something. Like Carl, I am wondering how your cya can be 60 if you drained and refilled. My question ---- did you totally drain or just do a partial drain?

Also, if you are fighting something in the water, which you must be since the chlorine is disappearing, then you need to test a minimum of twice a day and more than that is even better and will clear things up faster. Each time, add enough bleach to raise back up to shock level. The key to killing algae is to sustain the high cl level and not let it yo-yo up and down. Otherwise, it will take forever to get it cleared up. If you can test 3, 4, 5 times a day and each time shock it back up, all the better.

Welcome to the forum!

[bri12]

Watermom,

Yes, I did a partial refill, about half. My original CYA test was over 110. Like I said earlier, after reading alot in here, after finding your forum, I realized that I needed to lower the CYA by draining and refilling.

I used quite alot of bleach after refilling with the idea of getting it to shock level of around 20 to 25. Water was a stale green cloudy combination. I kept adding bleach, but couldn't seem to get FC up high enough, which is when I posted. Testing with a Taylor 2006 kit.

But now the water is blue and not cloudy. Actually, it's looking pretty good. So I'm assuming I don't need to get to shock level now? I'm testing twice a day, and FC is around 3.5. Also, I'm seeing recurring small sudzy patches on top of the water. Is this normal? Just making sure of how I should proceed.

Anyway, love your forum, and appreciate any input. I'm a believer for sure.

Oh, and I'm in South Florida...we don't close for winter...

[aylad]

Test your water for chlorine tonight after the sun is off the pool and again in the morning before the sun is on it--if you've lost less than 1 ppm chlorine, then you can let your Cl stay down in the 5-10 range, but don't let it go less than 5 ppm or you're going to have algae problems again. If you're still losing 1 ppm or more chlorine overnight, then you're not through fighting what's in your water and you need to bump it back up to 20 ppm.

I would use strictly bleach over the winter, and allow your CYA to come down further through frequent backwashes and rainwater refills so that you don't have any algae problems that are CYA-related next year.

Welcome to the forum!

Janet

[bri12]

Will do, Thanks Janet