FC daily usage

[Katana]

Here in PA, we had a "Heat wave" of 90+ days for 3-4 straight.

My nomal FC usage until then was 1.6-2.0ppm...

During the heatwave, it jumped to 3-4ppm...3.8ppm the one day. I'd add to get it up to 8.8 or so...and by next day, sun down I'd be at 5 again.

Pool temp was 84, bright sun...no bathers except me and the wife for an hour or two.

My water is clear...I have passed the OCLT...0.4ppm per night.

My CYA a is 60-70ppm so I am maintaining with CL at 5-10ppm with liquid chlorine (12.5%). I am converting to liquidator soon...right now it is manual adds every night.

TA is 100, CH 200, Ph 7.6, CSI -0.03

Sound normal? I thought it was a tad high for a 17k pool....

 

[JasonLion]

That is a bit high if no one was swimming, but if a couple of people were swimming that day it is reasonable.

 

[Bama Rambler]

3 to 4 ppm isn't too bad if the sun is really strong. It is a little more than I would expect with the CYA that high, but not much higher.

How much debris do you get in your pool?

 

[chclark]

I also live in PA.... same deal.... my pool CYA is 60 and during those few days at 90+... FC 3-4 ppm usage a day...

 

[Katana]

3 to 4 ppm isn't too bad if the sun is really strong. It is a little more than I would expect with the CYA that high, but not much higher.

How much debris do you get in your pool?

Not much over these really hots days. The 280 was clear...just a few pine frawns. Normally, I do get more depending on the wind level. I try to keep the skimmers and 280 cleaned at least twice a day on those windy days because I know things start to break down quick.

I even backwashed yesterday to make sure all the "spring junk" was out of the filter and not in there decaying.

I also live in PA.... same deal.... my pool CYA is 60 and during those few days at 90+... FC 3-4 ppm usage a day...

Well that makes me feel a bit better. Today was cloudy with rain showers, I'm hoping it comes back down to something reasonable.

 

[Katana]

OK, post heat wave, pool still running up to 83 degrees from sun...still losing 4 ppm.

Adding 80oz of 12.5% per day. Chlorine going from 5 to 9 each day.

I did an overnight and lost .4ppm and water is very clear. I can see screw heads in my main drain clear as a bell.

Debris is minimal as the Spring dump is almost over, skimmers empty, Polaris empty. Running pump 10-12 hours per day.

I calc my equivalent puck usage would have been about 7-8 per week...and I don't think I was using that many.

Does the liquid chlorine not hold up as well as the pucks?

Am I missing anything?

 

[chem geek]

The chlorinating liquid and the pucks both result in the same chlorine in the water. The difference is that the pucks add to CYA so if the CYA was higher than the amount of chlorine loss may have been less. Also, you may have had a lower FC target when using pucks and the FC loss is a percentage amount of the FC -- so a lower FC loses less quantity of chlorine than a higher FC (at the same CYA level).

Anyway, since you aren't losing much overnight but are losing more during the day, then you could have your CYA be higher and your FC proportionately higher with it. The absolute FC loss drops due to some complex CYA protection that isn't fully understood (non-linear effects). 80 ppm would be the high end and usually that's only for very sunny areas like Arizona so it's a bit odd to have such a high chlorine demand in PA.

You say you noticed the jump during the heat wave so maybe the combination of very sunny days and warmer water temperature is creating more chlorine demand, but even so 4 ppm seems high (not unheard of -- there are a few users with high chlorine demand, but most are more like 2-3 per day).