Just refilled pool - should I do a non-clorine shock first or just clorine shock?

[Oly]

Post a pic for us when you get it open.

We can use it to convince future troubled pool owners to check their ladders before SLAMing.

 

[mjustison]

Took the ladder out. There were no immediate signs outside of the cloudy plumes that shot out while removing it from the pool. I shocked last night and got it up to 17ppm (I overshot a tad for my CYA level).
This morning it was still down about 1-1.5 ppm. I imagine the latent algae that exited the ladder was still consuming the chlorine. I vacuumed and cleaned the filter this morning and hoping for not so drastic of a drop tonight.

 

[mjustison]

I swung home for an afternoon check in. The Cl levels dropped off from about 15.5-16 this morning to about 11 just now. Water looks clear and there's no visible sign of algae. I'm guessing they're either still consuming Cl and haven't been fully eradicated or my CYA levels are still low (I really can't imagine I'm that off base with them).
It hasn't been very warm at all today - about 76 degrees. I'm not sure I can blame the Cl loss to sunlight and lack of stabilizer. Unfortunately I only have enough CYA reagent to test maybe twice more. The refill is in the mail and won't arrive till next week.
I tested my water at Leslie's yesterday and they quoted me a CYA level of 35. The only thing is is that they kinda screwed up my pool volume. It's 7600 if filled to 4ft but I'm only filled to 3.5 ~ 6600 gal. Would that skew their numbers at all? I figure they're testing roughly the same way I'd test. (Cloudy water, black dot, etc)
I'm reluctant to keep adding CYA till I know it's not user error. Is it more likely that my Cl loss is still due to organic components that haven't been killed yet?

Thanks!

 

[mknauss]

It is sunlight on the pool and not the air temperature that burns FC off. So you probably have some UV loss.

I would not trust the pool store test. They rarely do it outside, with sun to their back, etc - or worse - they use an electronic tester that may not have been calibrated properly.

Trust your numbers. And not a big deal if you are slamming. I would use 40 ppm CYA or FC of 16 for shock if you tested CYA at 35 (round up, the scale on the vial is not linear).

 

[mjustison]

It is sunlight on the pool and not the air temperature that burns FC off. So you probably have some UV loss.

I would not trust the pool store test. They rarely do it outside, with sun to their back, etc - or worse - they use an electronic tester that may not have been calibrated properly.

Trust your numbers. And not a big deal if you are slamming. I would use 40 ppm CYA or FC of 16 for shock if you tested CYA at 35 (round up, the scale on the vial is not linear).

Okay, thanks. I'll test my CYA again tonight. I have some hth test strips that I could stand to get rid of, I'd rather waste them and be somewhat in the ballpark than waste my cya reagent.

 

[mjustison]

This morning I tested again. Looks like the first time it hasn't dropped more than 1ppm overnight. It was a bit hard to judge but my loss was somewhere between .5 and 1ppm. I think that I've gotten over the algae. I'll do another overnight test to be sure.

 

[mjustison]

Thanks again for all your help. Last night I showed no significant drop in Cl.
It's been about two weeks now and I only see about (maybe) 35 cya. I dropped another 10oz of Clorox brand stabilizer into a sock. I hope I'm not being impatient only to find out next month I have a cya of 100. Does this stuff usually take a while to take effect?

 

[JimMarshall]

Thanks again for all your help. Last night I showed no significant drop in Cl.
It's been about two weeks now and I only see about (maybe) 35 cya. I dropped another 10oz of Clorox brand stabilizer into a sock. I hope I'm not being impatient only to find out next month I have a cya of 100. Does this stuff usually take a while to take effect?

I believe it can take up to a week to show up on a test after addition.