Difficulty Maintaining FC and Scale Issues

[acastal]

I have a SWG and have had issues maintaining chlorine in my pool all summer. I discovered my pool service was adding chlorine tabs because the chlorine keeps testing at 0, but that still wasn’t keeping the chlorine level up. We had them test the salt cell, which showed it wasn’t working correctly and we replaced it. We keep bumping up the % the salt cell is working and still not helping. We are now using the SWG and chlorine tabs and still less than 1 FC (generally 0-.5). CYA keeps going down and then we bring it back up (or the pool service does). The water looks mostly clear at the moment, but it has been a little cloudy and a bit green at times and there seems to an oily film on top. I’m thinking we need to shock the pool at this point. Here are today’s numbers:

Calcium 600 (I know this is really high - see comment on scale below)
Ph 7.5
FC .5
CYA 60

If I shock the pool, how much chlorine should I have on hand for a 16k gal pool? Also, we have always had issues with scale, particularly when we increase the salt cell %. Our water is softened so that’s not the issue, and we now have a new cell so that’s not it either. What could be causing the scale?

Thanks in advance.

 

[ajw22]

What test kit do you have?

Do a Overnight Chlorine Loss Test with your SWG off and tablets out of the pool.

We don't use shock...



Post a complete set of water chemistry and calculate your CSI using PoolMath

FC
CC
pH
TA
CH
CYA
SALT
WATER TEMP
CSI

Calcium Saturation Index (CSI)

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[acastal]

I meant to say slam, not shock. I'm using the TF-100 test kit. Since we can't seem to get FC above .5, I'm not sure what the OCLT will tell me? Here are the other current numbers:

FC .5
pH 7.5
TA 130 (I just tested this after I added some chlorine so it may be off - this was 90 less than a week ago)
CH 600
CYA 60
SALT 3500
WATER TEMP 89
CSI .27

 

[ajw22]

Your scale is likely caused by your high CSI. We can talk about how to deal with that after you complete the SLAM Process. @mknauss advises on how to deal with high CH in your region.

Start the SLAM Process. For CYA 60 your SLAM FC will be 24. A gallon of 10% will raise your FC by 6. I would get at least 12 gallons of 10% to start and see how quickly you burn through it.

 

[mknauss]

Welcome to the forum!
As Allen says, deal with the SLAM first.

TA will need to be reduced to get your CSI back to negative.
I suggest you read ABC's of Pool Water Chemistry.

 

[acastal]

I'm in the middle of the SLAM and made several mistakes and have some questions. First, I overshot the FC and it's at 37. I was testing regularly so not sure how that happened. Second, I just tested the CYA and it is down to around 40. What would cause it to decrease? I also added a bag of chlorine granules from Leslie's at the beginning (they really pushed it saying it was much stronger), before I realized it has stabilizer in it. But it seems that would raise CYA and not lower it, right? Finally, I also stupidly added some Phos Free that the pool company left behind thinking that would help, and it just made the pool really cloudy. What should I do now? Just wait and see what happens?

 

[ajw22]

Just continue with your SLAM. Let your FC drop down to 16 and maintain it there.

The coudiness will clear in time.

Stay out of pool stores.

 

[acastal]

This morning it's down to 16.5 FC. Ajw22 - You mentioned maintaining it at 16. Based on my CYA before the SLAM, I thought I was aiming for 24. Should I bring it back up to 24 until I pass the OCLT?

 

[ajw22]

This morning it's down to 16.5 FC. Ajw22 - You mentioned maintaining it at 16. Based on my CYA before the SLAM, I thought I was aiming for 24. Should I bring it back up to 24 until I pass the OCLT?

You said in post #6 that your CYA now tested at 40. Maintain the SLAM FC level for your current CYA level.