What FC Loss To Expect

alanrmeadows

LifeTime Supporter
May 5, 2010
137
Here are the details:
South Arkansas
97-100 Degrees
Not much shade
17,500 Gallon Fiberglass Inground Pool
CYA of 40

What would you expect the daily FC loss to be assuming no organics and no swimmers? Is losing 3ppm per day way too much or possible and even probable during times of intense heat?

Thanks,
Alan
 

woodyp

Mod Squad
TFP Expert
LifeTime Supporter
Apr 17, 2010
10,286
East Texas
FULL sun all day here too. Heat stroke days, high humidity, warm water---------I average 3.5 with CYA of 50. Target is 6 on the chlorine/cya chart and minimum for that is 4. I take mine to 8 to maintain minimum bottom number and a little cushion.
 

Jersey Devil

Platinum Supporter
Aug 4, 2007
61
Jackson, NJ
I am in NJ and it has been hot and sunny most days. I average 3 ppm FC loss with normal bather load. That has been pretty consistent over a CYA range of 30 -50 ppm. Every pool is different and you just have to get comfortable with your own results. Luckily bleach is cheap!
 

257WbyMag

TFP Expert
LifeTime Supporter
Feb 23, 2008
5,061
Denton, TX
As hot as it has been, a 3 ppm loss over the course of a day sounds about right. Have you considered bumping your CYA up a little more? That might help some and is exactly what I have done this year.
 

astrolite

Active member
Jun 25, 2008
31
Lewisberry, PA
phildesantis said:
That has been pretty consistent over a CYA range of 30 -50 ppm. Every pool is different and you just have to get comfortable with your own results. Luckily bleach is cheap!
Amen to the every pool is different! South Central PA, one swimmer normally, 7 hrs full sun, 84 degree pool temp, lots of trees, oak, maple and pine, cya at 50, <0.5cc, overnight loss 0.5 to 1.5ppm. Can't seem to get mine below the 5-6ppm per day range even after shocking the heck out of it. Pool is crystal clear. I'm pretty convinced I've just got a steady influx of organics from the trees.

So I'd say 3ppm is great!
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
astrolite said:
... lots of trees, oak, maple and pine, cya at 50, <0.5cc, overnight loss 0.5 to 1.5ppm. ... I'm pretty convinced I've just got a steady influx of organics from the trees.
With such a high overnight loss, I'd say your assessment is right on. You might try using skimmer socks that you clean regularly to try and capture and remove the debris from the pool more quickly and see if that helps. Of course, a pool cover is another option though you'd likely have a mess on top of the pool cover to remove every time you'd want to open/remove the cover.

Note that larger debris, such as leaves, isn't going to have as much of an effect on chlorine demand as small particles such as pollen or seeds (the soft kind that float in the air).

One more thing to note -- check your filter to make sure there isn't a lot of debris or possibly biofilm in it, though that's less likely with DE than with sand. You could also check behind light niches and under removable ladders just in case there may be yellow/mustard algae.
 

astrolite

Active member
Jun 25, 2008
31
Lewisberry, PA
chem geek,

I'm thinking more likely pollen than debris; I don't get that much large debris this time of year.

The other possibility is red slime; I've been fighting that the last two years in a row. Pulled my ladder earlier this season and it was all over the bottom of it. Used some straight 6% bleach and a toothbrush, what a pain! Pulled off my skimmer plate and cleaned behind there. Don't have any lights or anything else. Threw all my pool toys in the pool while shocking. Bleached my swimming trunks. Concerned it could be growing in my return lines. Regularly dump chlorine in my skimmer to treat the filter and lines the best I can. Not sure what else to do along those lines. There is none visible but I don't suppose that necessarily means there's none there.

At least the pool is crystal clear and from what I've read red slime is not dangerous to humans!

alanrmeadows, sorry didn't mean to highjack your thread.
 

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