SLAM FC Readings... Pass or Fail?

[OGSW20]

I am having some trouble with my FC readings. I started a SLAM five days ago. First OCLT on 9/17 was 4.5 and in the morning it was 2.0. That is when I initiated a SLAM.

9/18 OCLT 22 PM 21 AM based on 10ml sample
9/19 24 PM 20 AM 5ml sample
9/20 30 PM 29 AM 5ml sample
9/21 26 PM 24 AM 5ml sample
9/22 21 PM 20 AM 5ml sample

Why do I keep passing and then failing? When I did the test on 9/19, I just eyeballed the sample water at the 5ml mark. Since it was such a small sample, I was worried I did not measure the water sample correctly, so the rest of the tests from 9/20 on, I would be using a 5ml sample and measured with the 1ml dropper to make sure I had exactly 5ml in the test sample. Water is crystal clear and CC is below 0.5. Do I continue with the SLAM or would you consider this done?

Also, I should add that after a full day of sun with 90 degree weather and SWG turned off, I would lose about 3ppm FC during the day. I think that probably sounds about normal for daily FC loss with full sun.

 

[ajw22]

There are 3 exit criteria for the SLAM Process

You are done when:

• CC is 0.5 or lower;
• You pass an OCLT (ie overnight FC loss test shows a loss of 1.0 ppm or less);
• And the water is clear.

 

[OGSW20]

What about the pass, fail, pass, fail, pass on the OCLT? Why does it keep going back and forth?

 

[beautifulpool]

What about the pass, fail, pass, fail, pass on the OCLT? Why does it keep going back and forth?

It means you’re making process, but you’re not home yet

 

[beautifulpool]

What about the pass, fail, pass, fail, pass on the OCLT? Why does it keep going back and forth?

I take back my comment on almost home, since I misread your latest readings.
You may have already arrived.

 

[ajw22]

If you continue passing the OCLT using at least the 10ml test then you are good.

I think the 5ml test introduces too many errors with the small sample size to be precise enough for 1 ppm in 20.

Let your FC drift down to 10 and check your OCLT there.

 

[mknauss]

Also, the OCLT should be done with a 10 ml water sample. The error when using a 5 ml sample is quite high.

 

[OGSW20]

If you continue passing the OCLT using at least the 10ml test then you are good.

I think the 5ml test introduces too many errors with the small sample size to be precise enough for 1 ppm in 20.

Let your FC drift down to 10 and check your OCLT there.

Thanks, I will let it drift down and try the OCLT again. I read another thread that suggested a 5ml sample was OK to do. I was just trying to save on some reagents. Dropping 50 drops sure does use it up fast!

 

[duraleigh]

Dropping 50 drops sure does use it up fast!

Yes, it does, but it's chump change compared to the cost of your pool and cost of your life style........not even worth factoring in.

The 5 ml sample, however, wastes your time and even perhaps some of your money because you pass-fail so often. Do the 10 ml as Marty and Allen suggest. You'll never look back.

 

[OGSW20]

Last night's and this morning's readings were 14.5 then 13.5 with a 10ml sample, cc is at 0. Should I do one more 10ml sample test tonight and in the morning or do you think I'm safe?

 

[mknauss]

As long as the pool is crystal clear, you are done.

 

[OGSW20]

As long as the pool is crystal clear, you are done.

Thanks Marty. It has been crystal clear since day one even before the SLAM process started.

 

[wilafur]