Chlorine issues

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G

geewiss

Bronze Supporter
Jul 23, 2020
49
Centreville Maryland
Second year pool owner and this is the first time I'm having issues with the Chlorine levels.


I shocked the pool with non chlorine shock about 5 days ago due to high combined chlorine levels. At this test I think the reading was around 2.4.
I waited a day and then tested again and for some reason the combined chlorine went even higher. Don't recall the number.

Yesterday afternoon I decided to go to my local pool store and get the water tested. They had me add 4 lbs and 3 oz of CAL-SHOCK due to still a high combined chlorine level. I added yesterday evening and let the pump run all night.

Took water back to pool store and now the readings seem worse.
FC = .89
TC = 9.41
CC = 8.52
PH = 8.2 - I just added acid and re-tested and I'm now at 7.3
ALK = 90
CYA = 47
Iron = .1
PHSPHATE = 350

Odd thing is that the pool doesn't really smell and is crystal clear. I'm reading that the non-chlorine shock can give false TC readings. Is that true and would it cause these fals high reading for days after?

I'd appreciate any feedback on this as I'm puzzled at this point.
 
Merged threads - TFP Mod

I think this is a basic question but I can't find the answer using the search function.

I seem to have an issue with Chlorine and I can't find the calculation on how much non chlorine shock (in the swim chlorine-free oxidizing shock) to use to bring down the combined chlorine. Or should I be using straight bleach as I've seen some others do. Please advise...I need help! Thanks in advance!

FC = .89
TC = 9.41
CC = 8.52
PH = 7.3
ALK = 90
CYA = 47
 
Welcome to the forum!
Your issue is you used MPS (non chlorine shock) in a pool. There is no reason to do that.
Your CC will read very high until that is consumed.
What does your water look like?
TFPC uses the SLAM Process to clear the pool of organics. You need a FAS-DPD test kit to manage your pool water chemistry.
I suggest you read ABC's of Pool Water Chemistry.
 
The pool looks absolutely clear and I don't have a chlorine smell either.

Is it bad to use a MPS? I used it to lower the total chlorine reading. I read that it's ok to use this as you can swim shortly after adding it.

Any idea on how long it will take for the MPS to be consumed? Is it safe to swim like this? I turned up the SWG to raise the FC. Hopefully thats ok.

I'll have to order that test kit. I thought I did good when I bought the lamotte but I guess not.

Thanks for your input
 
It is safe to swim with a FC up to 20 ppm with your CYA. The CC is not from ammonia based organics so it should not smell.

MPS is not good as it adds sulfates to the water. Just do not use any more of it. Chlorine is all you need.

The Lamotte is known to not test CH accurately. The TA modules they had issues with recently.
Read Pool Test Kits - Further Reading
 
mknauss said:
It is safe to swim with a FC up to 20 ppm with your CYA. The CC is not from ammonia based organics so it should not smell.

MPS is not good as it adds sulfates to the water. Just do not use any more of it. Chlorine is all you need.

The Lamotte is known to not test CH accurately. The TA modules they had issues with recently.
Read Pool Test Kits - Further Reading
Click to expand...

So you are thinking that as the MPS wears off that my CC will drop?

Just ordered the FAS-DPD test kit.
 
It appears to be coming down but it's been 3 days since adding the MPS. The readings are now as follows...

FC = 2.89
CC = 6.42
PH = 7.2

Do you think that waiting more time will lower the CC even more or is 3 days enough and now is the time to SLAM the pool? Pool is still crystal clear blue.

Also, I bought some standard bleach. Do you think I should add some to bring up my FC and not have my SWG working so hard as it's on 80% with pump running 14 hours a day.

Thanks!
 
I have not done the Overnight Chlorine Loss test as of yet, but I can if that's recommended.

I thought I read that if your CC is >.5 then a SLAM is recommended. Is that not the case? Are my CC numbers not an issue?

Bare with me, I'm trying to get educated, just a little slow :)

Again, thanks for all the help!
 

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CC is an indicator. But you artificially increased them using MPS. And one test of high CC is not something to react to unless you fail an OCLT and your pool is cloudy and turning green.

What does your pool water look like?
 
Ahh I see.

My water is a perfectly clear beautiful blue :).

I was just concerned that it's been over 72 hours and my CC is so high.

What would you think about me adding some bleach to bring up the FC to not have my SWG working so hard?

What would you recommend at this point...just give it a few more days?
 
Absolutely. Plain liquid chlorine. Be wary of household bleach. Most have additives.

Maintain your FC in the target range for your CYA. Test CC every day to see that it is declining.
 
I'm waiting for my new TFP recommended pool kit to come in before doing the Overnight Chlorine Loss Test but in the meantime I've been using my Lamotte tester to keep an eye on the CC. I would of expected the CC to have dropped off some more by now (4 days since adding the non-chlor shock). Have you ever seen MSP to take this long to disperse?

Keep in mind these results were from the Lamotte so not as accurate my new test in the mail.
FC = 2.98
CC = 6.51
PH = 7.3
ALK = 55 (added some baking soda just now to raise this a tad)
 
You showed a TA of 90 earlier, have you been adding acid between then and now? That is the only way TA goes down.

Hard to say on the CC. If the MPS has nothing to react with, it will stay in the water. Let's see what your FAS-DPD says when you get it.
 
I did have to add acid since my PH read 7.9 the other day. This is only the second year of the pool and the PH is still naturally rising quite frequently.

I looked all over the place for the lamotte MPS OUT reagent but can't find it anywhere. I'm pretty sure that the kit I just ordered ( K-2006C) doesn't have an MPS out reagent, so I'm afraid I don't have a way to determine if it's a false reading or not.

Not asking for a chemistry class explanation as I'm sure you have many other better things to do :) but what does the MPS react with? I'm assuming contaminants? I don't have a heavy swimmer load but I do find many small frogs (sometimes up to 7 a day) in the skimmers.
 
One addition of acid would not have dropped your TA by nearly 40 ppm. I suspect test error in that TA reading.

MPS is an oxidizer. Not a sanitizer. So it has to find something to oxidize to be consumed. Typically that is bather waste, animal waste, etc. It is used in hot tubs for that, as they have small water volumes.
 
mknauss said:
One addition of acid would not have dropped your TA by nearly 40 ppm. I suspect test error in that TA reading.

MPS is an oxidizer. Not a sanitizer. So it has to find something to oxidize to be consumed. Typically that is bather waste, animal waste, etc. It is used in hot tubs for that, as they have small water volumes.
Click to expand...

Understood. I'm throwing this tester away when the new one gets here. I wish I would of found this forum a while ago :)

I really appreciate your help and I'll let you know what happens when the new tester gets here.
Thank you!
 
Test kit hasn't arrived yet but I've been doing some reading in this forum.

I also failed to mention earlier that my pool builder used two 10lbs containers of Jacks Copper and Scale (on July 7th) to try and remove staining out of the Luna Quartz finish. Ever since then, I've had issues with Chlorine. I just found other threads on TFP where they had the same issue so my issue seems to be due to this Jacks stuff. No idea how long this is going to skew my FC readings but I'm still digging and patiently awaiting my new test kit.
 

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