Acceptable chlorine loss over 24 hours

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denniswiseman

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Bronze Supporter
Nov 27, 2014
235
United Kingdom
Hi
My pool is covered and I have a thermal blanket so no UV degredation and no bather load
Because I'm getting low on reagents (already ordered) I am only testing once in 24hrs
I have a chlorine loss of 1.5ppm in 24hrs. Would that be acceptable to pass the OCLT
 
Hello! Well, remember that an OCLT (Overnight Chlorine Loss Test) and the amount of FC lost in 24 hours are two different things. If you only lost 1.5 FC in 24 hours (example 5:00pm 23 Mar to 5:00 PM 24 Mar), that's great. But if you lost 1.5 FC from dusk to dawn (say 9:00PM to 5:00 AM) that's not good. Make sense?
 
Hi Dennis. IMHO, the OCLT is only valid when tests are taken from dark til dawn, 8ish hours, meaning 2 tests. Anything else is a guess.

With that said, I would not be alarmed over a covered pool losing 1.5 ppm n 24 hours UNLESS I had other indications of nascent algae, eg. Slight cloudiness to water.

So I guess my question is why are you wanting (but unable to) perform the OCLT. Have you been slamming?
 
Hi Texas Splash and Swampwoman

The loss was over 24hrs
The water is clear but I have been having trouble maintaining chlorine after AA treatment and only now does it appear to stabilise
I was concerned that I may have had some invisible algae and I slammed the pool
I'm very low on reagent and it's not due untill the 3rd of april so I want to be frugal with the testing
 
Hi Dennis. I realize its too late for the advice but so you know next time, don't slam after an AA treatment (unless youre POSITIVE you need to) as it wears down the metal sequestrant and risks returning of the staining.

Leftover AA always fights chlorine until its broken down by same, so the trick is just to keep topping it up until stable. Between now and when you get your reagents, just be sure to maintain you FC to TFP regs and you should be fine ;) There is no need for an OCLT at this time.
 
When I finished the AA I kept the chlorine to the minimum as per the instructions for 2 weeks added sequestrant but it still wasn't holding
That's when I started the slam
The FC is at 7 now, ill drop it to 5 and add more sequestrant


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