fc dropped to 0 overnight. must I slam????

[cubbieblue]

Hi folks,
Thanks in advance for any advise.
2nd season in. Water has been balanced and maintained for 3-4 weeks. Chicago just had heat wave, blazing sun and we had 2 pool parties in 2 days. This morning i got a 0 fc reading and added appropriate bleach to bring to correct level.
My concern is whether I need to slam as a result of 0 fc for short period. Sun and use obviously consumed it quicker than normal. Still crystal clear but wanted to err on side of safety for use today. Any quick help would be greatly appreciated.
Whew its hot out there.

Thanks!!!!

 

[mknauss]

Overnight Chlorine Loss Test

Do one tonight. You might go to 15-20% of CYA for FC right now to get ahead of it.

 

[YippeeSkippy]

When in doubt-perform the Overnight Chlorine Loss Test to determine if you have anything brewing in the pool.

Pool School - Perform the Overnight FC Loss Test (OCLT)

Anytime you have large pool parties, up the FC before and after just to be sure it doesn't drop to zero.

Maddie

 

[cubbieblue]

Thanks for quick reply!!!!
Not sure what you mean by the cya suggestion, sorry. Could you clarify that for me.
Am i good to swim today in mean time? Will slam tonight.

- - - Updated - - -

Thanks for quick reply!!!!
Not sure what you mean by the cya suggestion, sorry. Could you clarify that for me.
Am i good to swim today in mean time? Will slam tonight.

 

[mknauss]

Whatever your CYA is, raise your FC to 15-20% of it. So if the CYA is 50 ppm, raise your FC to between 7.5 and 10 ppm.

 

[cubbieblue]

keeping fc at 7 with cya at 40 so think I'm there.
Do you think swimming now is OK?
Thanks again for help!!! People like you guys are what makes this the best site out there!!

 

[cubbieblue]

so fc is at 7 now with 0 cc.
Opinions on ok to swim???

 

[YippeeSkippy]

Yup, go swimming.

But that doesn't necessarily mean nothing started growing in the pool while the FC was low. Hence we still suggest an OCLT to be sure.

And have you seen this yet?? --> [FC/CYA][/FC/CYA]

Maddie

 

[cubbieblue]

Thanks for reply again. They are in pool now. yippee!
Yes I've seen chart and use pool math app for all my maintenance. Were you suggesting 7 might be high?
I'll do the oclt tonight. Wouldn't cc above 0 give me an indication though of something brewing? What would the difference be in those 2 evaluations?

 

[DeanP66]

Generally CC of .5 or less is fine. If it gets to 1 or greater, that is generally an indication that something is growing in the water. If after running your OCLT, you find that you only lost 1 PPM or less FC and your CC is .5 or less, I'd say that you can forget about the SLAM and just keep your FC in line with the FC/CYA chart. If your CC's are 1 or more though, I'd do a SLAM just to make sure. It may only take a day finish it. Just do another OCLT and CC test again the next day.

 

[YippeeSkippy]

No, not high at all based on CYA you mentioned.

Not all problems show up in CCs. Many (most?) do, but since you let your FC go to zero, we just want to rule out anything brewing. Do the OCLT and if you lose 1ppm or less of FC overnight you should be just peachy!!

Maddie