Pool eating FC!

Whjr15

Member
Jul 6, 2019
5
NE Ohio
Hi guys! Just wanted to say, again, how awesome this site is. It’s truly an invaluable resource!

Anyway, after having my pool up for about a month now (24’ round AG 52”), with the help of this site, I’ve been keeping it maintained without the major hassle I went into it expecting. However, I've come across something that I would like advice on.

This morning (about 7 hours ago, from this posting), I added 10% bleach to achieve a FC of 21. (Pool math app must’ve glitched out on me, because I was shooting for 7!) The problem that I’m observing is that, a little over 7 hours later, with no swimming, the FC dropped to 15.5. Is an FC loss of 5.5 in 7 hours normal? From what I’ve been reading on here, I suspect not. Water is also brilliantly sparkling, with no visible indication that anything is wrong.

Other relevant info:
CYA: 40
CC: 0

Thanks!
 

jblizzle

Mod Squad
TFP Expert
LifeTime Supporter
May 19, 2010
43,255
Tucson, AZ
With a CYA of 40ppm, I would not be surprised if you lost up to 50% of the FC to the sun in 1 day if you have a lot of exposure.
 

Whjr15

Member
Jul 6, 2019
5
NE Ohio
I tested it using the tf-100 kit. The pool math app sometimes gives me drastically different suggested amounts, and I’m not sure why. It’s never been THIS big of a discrepancy, but I’ve always caught it & double checked before adding anything.