Liquid chlorine use after SLAM

[beckyspuds]

I'm a longtime pool owner struggling to maintain an adequate FC level. I converted to Chlorine tabs last year when the cost of Bromine went skyhigh. I had no problems last year. I opened this year and have been dealing with severe algae- nothing I was doing would help. A friend referred me to your site and the SLAM process. I had my water tested and found I had a CYA of 189! Used the drain and refill method until my CYA was 70. I then completed the SLAM process. My water is crystal clear now. My question is when I test every evening it shows no FC. My CYA is 50 so I have been adding liquid chlorine for a target FC of 7-8. I usually add a gallon and a quart. The next morning my FC is still 0. Will I continue to need adding that much liquid chlorine every night? I was thinking that the amount would gradually decrease to a few ounces. I have a 30' round above the ground pool- 21,000 gallons. Any suggestions appreciated! Thank you! Becky

 

[ajw22]

Welcome to TFP.

What test kit are you using?

Does your pool pass the Overnight Chlorine Loss Test ?

 

[PoolStored]

You probably have something lurking. It is likely you let FC get too low for your CYA. Always follow this...Link-->FC/CYA Levels

What test kit do you have? If you don't have a recommended kit, order that now. Link-->Test Kits Compared

To address your current problem, do this test when/if you have a kit. Link-->Overnight Chlorine Loss Test

If you fail, SLAM. Link-->SLAM Process

 

[Endro32]

SLAM isn’t technically done until you pass the Overnight Chlorine Loss Test while still at SLAM level. Was that the case and it’s since gotten this bad?

 

[PoolStored]

SLAM isn’t technically done until you pass the Overnight Chlorine Loss Test while still at SLAM level.

You don't have to be at SLAM level. You should be at or above 3FC.

 

[Endro32]

You don't have to be at SLAM level. You should be at or above 3FC.

That's true, but if her pool didn't pass the OCLT before she let the chlorine return to normal from SLAM levels, then she wasn't fully done with the first SLAM and that would explain what's going on. That's all I'm asking about.

 

[beckyspuds]

Sorry for slow response- I have used the Taylor OTO 6 way test in the past. I did get the FAS-DPD test and have been using it. I have been doing the OCLT and passed a couple of days- but not consistently. Should I be using a Target FC of 3?

 

[PoolStored]

Here are your targets…link—>FC/CYA Levels

 

[beckyspuds]

Last night I tested at 9p- FC 0. I added 1 gal of 12.5% liquid chlorine. Tested 30 minutes later and FC was 4. Tested this AM and FC was 4. I didn't add any liquid chlorine. How should proceed tonight? Also- my test at the pool store said my Calcium Hardness is 111 and said I need to add 36# of their product. Do you agree?

 

[PoolStored]

Raise your FC to 9 now. Test tonight and see where it ends up. How confident are you that your CYA is 50. Did you get that value from your own test kit?

If you don't have a full test kit, get one now. Link-->Test Kits Compared

I suspect that your CYA is actually lower and that is allowing UV to consume your FC.

You don't need to add calcium, not necessary in a vinyl pool.

 

[beckyspuds]

The test at the pool store on Friday showed CYA to be 67. I tested it here yesterday and it was 60. My grandkids are coming swimming at noon. OK for them to swim in FC of 9?

 

[PoolStored]

With a CYA of 60, I'd raise FC to 10. I would test during the day and keep it 9-10. Perfectly safe.

 

[beckyspuds]

Just tested it and FC is 4. Suggestions?

 

[PoolStored]

Did you not do additions during the day?

Raise it back to 9.

 

[beckyspuds]

No I didn’t- busy day! Will do! Thanks for your help!

 

[PoolStored]

If you raised it to 9, now you know that in the summer with lots of swimmers you can use up to 5FC, or more.

Your target range is 7-9. 7 (low end) + 5 heavy usage = 12.

Before another big day like today, dose to 12...you will be in range at the end of the day...

 

[beckyspuds]

Got it! I am going to shoot for maintaining it at 8. Should I be testing and dosing just at night or in morning too? I’m losing 1 overnight for the last 3 nights. Also, I’ve had to decrease my pH a couple of times because it was at 8. Is there a correlation between FC and pH? Last question- how does a heavy rain usually affect pool chemistry? I appreciate all your help!

 

[PoolStored]

Got it! I am going to shoot for maintaining it at 8. Should I be testing and dosing just at night or in morning too?

You can do both if you like.

I’m losing 1 overnight for the last 3 nights. Also, I’ve had to decrease my pH a couple of times because it was at 8. Is there a correlation between FC and pH?

No. Rising pH is due to a high TA. Don't worry about it, just keep pH in the 7s. When it rises to 8, reduce it.

Last question- how does a heavy rain usually affect pool chemistry? I appreciate all your help!

Not usually, but it can.

 

[dfwnoob]

Just to clarify what you wrote - When you say you "converted to chlorine", did you drain all of the water?

 

[beckyspuds]

Thank you!