Just opened my pool - 4.5ppm FC loss in 24hrs

[jgf310]

I just opened my pool - in doing so, i pumped out and replaced about 50-60% of the water

Pool is about 30,000 gal, i think, and made of cement.

after replacing the water, and testing it, I mostly played with CH and alkalinity, FC was low

Then, i added 1 Gal 12.5% bleach at night

The next morning( yesterday morning) i had:
pH 7.2-7.5
CH 225ppm
TA 40ppm
CYA 38 (From Leslies - I lost my view tube)
FC 6.0ppm
CC 0.5ppm
TC 6.5ppm

all good (more or less), right? CH and TA could maybe be a bit higher, but I will wait and see...

The next morning (this morning), everything is pretty much the same, except

FC 1.5ppm
CC 0.0ppm

That seems like a high 24hr loss - is it?
yesterday was pretty sunny...

Is my CYA too low? I hesitate to add any, because high CYA has been a problem - it's partly why i replaced the water - i am not sure i trust the Leslie's number, and i can't test myself until i replace (or find) the view tube.

my pool is pretty clear - nobody has been in it yet, there is no sign of algae, and the temp is pretty cold at 68, so i doubt the FC is being consumed by anything... I guess my CC=0 confirms this, right?

I added another gallon of 12.5%...

should i expect to use a gallon a day?

 

[splashpad]

If the pool is in full sun, possibly (CYA level)
But I would do a SLAM Process first, before raising the CYA level.

 

[jgf310]

why would you SLAM?

just because of the loss.., or is there something in the numbers that is off?

 

[Newdude]

Is my CYA too low? I hesitate to add any, because high CYA has been a problem - it's partly why i replaced the water - i am not sure i trust the Leslie's number, and i can't test myself until i replace (or find) the view tube

Hey JG. You know what to do, but for those who might not in future reading of this, That CYA tube needs replacing stat. Without it you won’t know where you fall on the FC/CYA LevelsFC/CYA Levels

 

[Newdude]

Without that info you won’t know where to keep the FC or where to raise it in case of a slam. 4.5 loss in sun and no CCs is probably ok but you wouldn’t hurt anything with a mini SLAM for peace of mind. It should go quickly if everything else is ok so far.

also, remember to flush out and scrub all the usual algea hiding spots

 

[ajw22]

Do a Overnight Chlorine Loss Test to understand if your chlorine loss is from the sun which CYA will help or algae which means the SLAM Process.

 

[splashpad]

why would you SLAM?

just because of the loss.., or is there something in the numbers that is off?

To eliminate any algae spores that may be present. If the Overnight Chlorine Loss Test shows no loss, then you know it's possibly not high enough CYA level compared to pool sun exposure.

 

[jgf310]

i will do the overnight test - but i have a question...

if the issue is just sunlight.., by sundown today, my FC will be low again, and i will have to add more bleach to get above 3.0ppm - the minimum for the test.

if i add a gallon of 12.5% before the test.., how long should i wait - letting it mix - before doing the baseline test?

i guess you would need to know about my pump.., and so on - how often my pool turns over.., but i don't really know anything about that...

is, say, an hour enough to wait after adding the bleach?

Do i run the pump all night when doing the overnight test?

 

[splashpad]

if i add a gallon of 12.5% before the test.., how long should i wait - letting it mix - before doing the baseline test?

Add the chlorine to the pool, with the pump running. Test FC 15-30min later (after sunset yes)

Do i run the pump all night when doing the overnight test?

No, but you can.
If you don't run the pump all night, the next morning ~ turn the pump on and wait 30min for the water to be circulated. Then retest FC level. If there is loss, than a SLAM Process is in order

 

[jgf310]

sorry to ask so many questions...

but just to be sure i am understanding things - is it likely that i have any issue with algae or other organics "consuming" my FC.., if my CC is consistently 0.0-0.5ppm?

i would have guessed - no.

and i have no problem doing the test, and even doing a SLAM, for insurance sake..,

 

[ajw22]

Yes, you can have algae with a CC of 0.

CC - Further Reading

www.troublefreepool.com

 

[splashpad]

sorry to ask so many questions...

but just to be sure i am understanding things - is it likely that i have any issue with algae or other organics "consuming" my FC.., if my CC is consistently 0.0-0.5ppm?

i would have guessed - no.

and i have no problem doing the test, and even doing a SLAM, for insurance sake..,

CC's gas off when the pool is not covered A lack of CC's just means the FC is doing it's job well! (or getting burnt up by the sun). That is what the OCLT tells us

 

[jgf310]

So, i did the overnight test

at 8pm - still some sunlight.., but not direct..., i had

FC=4.5
CC=0.0

at 7:30am.., light out but no direct sunlight.., i had

FC=3.0
CC=0.5

for a loss of 1.5ppm.., which indicates I should probably SLAM

cold-ish water.., pretty clear..,no sign of algae.., but do it anyway, just to be safe - right?

 

[ajw22]

You have algae even though you can’t see it.

 

[splashpad]

at 7:30am.., light out but no direct sunlight.., i had
FC=3.0
CC=0.5
for a loss of 1.5ppm.., which indicates I should probably SLAM
cold-ish water.., pretty clear..,no sign of algae.., but do it anyway, just to be safe - right?

Yup, it's a SLAM Process. Though by your numbers, it just might be raised FC levels for a couple days
Be sure to take a picture from the same angle at the beginning, during and after, the difference (even in "clear" blue water is really fun to see!)