OFCT question

[ngc4900]

Hi

I need some clarification on the OCLT. I have an indoor pool which has a vinyl cover when not in use. However, there are two sky lights in the ceiling of the pool room. I am not sure if the vinyl cover protects UV but I am waiting for an answer from Endless pools. If the cover blocks UV, then I would guess the “sun” factor is a non-issue?

I am on day 3 of SLAMing the pool . FC levels have been 13 for the first day and 24 for the last two days. I went ahead and raised the FC to Mustard Algae shock level just to be sure, however I do NOT think I have a mustard algae problem.

The problem I do have is that every time I do the OCLT test, the first FC I measure in the morning is 1 or 2 ppm lower than the prior night. Is the TFT FAS/DPD temperature sensitive? My pool is set at 87 F. When I retest with the same sample 5 minutes later, the 2nd FC measurement is identical to the previous night. My CC is zero or 0.5 or less. The water is clear. CYA 32.

Lastly, when does one start to balance the other parameters as the FC comes down after SLAMing. I know PH is will be off during shock FC levels. What about TA? CH? etc?

Thanks
Joe

 

[jblizzle]

If it is a solid cover, then it likely blocks the UV. Although having the cover on could be part of the reason the FC is dropping some as it oxidizes the cover and traps the CC.

That is not the process for mustard algae. Read the article in Pool School, you are just putting you pool and equipment at greater risk keeping the FC higher.

The FAS-DPD should not be temp sensitive.

You can adjust the other parameters whenever you want as the high FC does not affect them.

 

[Patrick_B]

That really sounds like test variation. It's not a temperature issue as that temp range is fine. You can be off a little with sample size, drop count, etc and have a slight change. If your weren't getting a later test (5mins) with the same as the previous night, I wouldn't say this.

I think you are done. Let it drift down on its own now so that you wind up at the proper FC/CYA ratio. What are your other current numbers that need adjustment?

 

[ngc4900]

Thanks for your help Jason. You are correct. I should have only brought the FC to 26 for 24 hrs. However, I did slam the pool at 13 and brushed, vacuumed and cleaned all toys three times. So if the cover is oxidizing some of the FC, the 1 - 2 ppm drop can be ignored and I can consider SLAMing complete with CC of zero?
Thanks

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I will measure a set of numbers and post them. However, PH will be off with the high FC correct.....?

 

[jblizzle]

yes, the pH will read artificially high.

 

[elwood58]

SLAM is not finished unless you have clear water.