Chlorine Consumption Rate

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michaelrbanks

michaelrbanks

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Sep 19, 2014
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Cibolo, TX
It seems to me I'm using more chlorine than I should, so I started tracking how my Fc changes over time. I started with trying to keep 3 PPM chlorine with 30 PPM CYA, but have since moved to 5 PPM chlorine at 40 CYA. The data is a bit immature at this time, but it seems like I'm adding more chlorine now that I'm at 40 CYA than when I was at 30 CYA.

Is this consumption realistic, or should I consider increasing the CYA? The pool sits in full sun all day & water temperature has been in the mid 70's. Consumption rates are shown in PPM / Hr.

data.JPG boxplot.JPG
 
well its hard to do that analysis until your pool temperature and outdoor temps are stabilized. increases in pool temp along with the increasing intensity of the sun are going to mean your FC consumption rate is going to be increasing no matter what the CYA level is. interesting analysis, but I think there are just too many uncontrollable variables for it to be of use right now. maybe in another month when things are more constant with sun/temps
 
Going on 6th year here now and losing about 4ppm daily with CYA at 50 or 60. No change in consumption rate when I added borates last summer as an experiment either. Pool full sun all day. It is what it is I guess!
 

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Saturn94 said:
About 4ppm FC daily loss here in SE VA. Full sun most of the day, CYA 70-80.
Click to expand...


I'm in Chesapeake. Last Summer I took my CYA to around 50 and my FC loss averaged 3.5 PPM. My pool has no shade. My CYA almost vanished over the Winter, probably because I stopped adding Chlorine when the water temp dropped below 50. I'm not complaining though...I've been slowly adding CYA using pucks. I like not having to use Bleach almost every day...makes me feel lazy. I plan to take my CYA higher this year (70?) to see if my FC loss drops compared to last Summer.
 
My pool only gets full sun about 4 or 5 hours per day. The rest of the time it varies from 25 - 50% shade. The chlorine consumption is pretty constant at 2 ppm/day with a CYA of 40. I've tried raising the CYA from about 30 to 60 ppm and the chlorine use does not seem to change enough to measure any difference.
 
Question about this. Assuming CYA of 40-50 still gives a loss of 4-5 FC / day. What is the advantage to keeping the CYA at that level?

If you put bleach in the pool in the morning and go to work. When you get home at night you might have zero to very little FC still in the pool. And now you have to bring it back up to 4-5 for the recommended levels.
But if you have much less CYA in the pool, say 0-20. You put the CL in the pool early. And when you get home, you will also have 0 FC. But at least the minimal / recommended FC is much lower.

It just seems like with those high FC loses, keeping CYA very low is cheaper over the long run.
I know Im missing the point. But can someone explain? :)
 
mitch08 said:
Question about this. Assuming CYA of 40-50 still gives a loss of 4-5 FC / day. What is the advantage to keeping the CYA at that level?

If you put bleach in the pool in the morning and go to work. When you get home at night you might have zero to very little FC still in the pool. And now you have to bring it back up to 4-5 for the recommended levels.
But if you have much less CYA in the pool, say 0-20. You put the CL in the pool early. And when you get home, you will also have 0 FC. But at least the minimal / recommended FC is much lower.

It just seems like with those high FC loses, keeping CYA very low is cheaper over the long run.
I know Im missing the point. But can someone explain? :)
Click to expand...

The higher the CYA, the higher the % of the FC that will be protected.
If you have 0 CYA, all your FC will be gone in a few hours.
If you have 30ppm CYA, you may lose 2/3 of the FC in 24 hours, targeting 6ppm you would be down to 2ppm (the minimum for your CYA) ... loss of 4ppm
If you have 50ppm CYA, you may lose less than 1/2 of the FC in 24 hours, targeting 7.5ppm you would be down to 4ppm ... loss of 3.5ppm

NOTE: numbers are a generalization and exaggerations to show the concept.
 
jblizzle said:
The higher the CYA, the higher the % of the FC that will be protected.
If you have 0 CYA, all your FC will be gone in a few hours.
If you have 30ppm CYA, you may lose 2/3 of the FC in 24 hours, targeting 6ppm you would be down to 2ppm (the minimum for your CYA) ... loss of 4ppm
If you have 50ppm CYA, you may lose less than 1/2 of the FC in 24 hours, targeting 7.5ppm you would be down to 4ppm ... loss of 3.5ppm

NOTE: numbers are a generalization and exaggerations to show the concept.
Click to expand...

That is why I believe a constant addition of a small amount of chlorine is better than slugging the pool once a day or adding it over a short period of time. When you add chlorine once per day you have to add enough to be sure you still have some FC available when you add it the next time. When using the liqudator or Stenner feed pump a small amount is added whenever the main pump runs and the FC stays mostly constant all day. It just seems intuitive to me that maintaining a constant FC is better than slugging it with a large dose one time then letting the concentration drift down.
 
I am asking,

For the correct CYA suggest for a pool, should we have a chart with the maximum hours direct sun exposure by day?

For now, we suggest the same CYA for a pool receiving 6 hours direct sun and another receiving 12 hours direct sun....
 

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