Chlorine Usage

[kenbob57]

Pool very clear but it has a larger Chlorine appetite. Trying to reduce Chlorine usage. I typically put in 1 gallon of liquid chlorine (12.5%) each evening which raises CL by 5 ppm. The next evening back at 4 ppm. Pump runs 24 hrs a day (20 hrs low rpm & 4 hrs high rpm after chlorine add). Pool seems to stay clearest at 8 to 10 ppm. Float 3 pucks a week in chlorine floater.

FC 4 ppm (before the 1 gallon add)
CC 0 ppm
ALK 120
PH 7.6
CYA 70

Any suggestions.

 

[JohnT]

At 70ppm CYA, 4 or 5 is too low for your chlorine. You should try to stay at 8 and never let it get below 5.

 

[kenbob57]

Thanks. What is most economical way at keeping at 8 ppm. 4 Gallons of CL cost me $10.00 so a week equals $17.50.

 

[duraleigh]

I would suggest performing the OCLT (it's in Pool School) The chlorine usage you indicate seems excessive and I think you have something living in your pool.

 

[jblizzle]

And always keeping pucks in the floater is continually increasing your CYA which is already on the high side. 3 pucks/week is almost 4ppm CYA increase per week.

Pull the floater. Do the OCLT. Shock if required.

 

[kenbob57]

I did the OCLT test. Results as follows.

Wed 6:15 PM the CL was 4.5 ppm.
Added a 1 gallon CL
Wed 8:30 PM the CL was 11.5 ppm.
Thur 5:45 AM the CL was 11.5 ppm.
CL stayed at same level through night

 

[duraleigh]

Only 2 things consume chlorine in your pool....sunlight and organics

Your first post, if I interpret it correctly, indicates you are losing 5ppm daily. The OCLT indicates none of that loss is at night so there is nothing organic in your pool to consume the chlorine. The ONLY thing left is that sunlight is consuming 5ppm of your FC daily.

With a CYA of 70, that chlorine consumption is at least double what I would expect based on reports here on the forum and I have absolutely no explanation for it.

 

[kenbob57]

Appreciate the quick response. I use the FAS-DPD method for CYA measurements. Is there a better CYA measurement method to get a better CYA as that is the only thing I can think of ... CYA higher than I am reading .... then I would need to drain some water to get the CYA back down.

 

[JasonLion]

The black dot test is the best available CYA test, though it does leave a lot to be desired. Take a look at the extended directions for some pointers on the best way to do the test.

 

[duraleigh]

Appreciate the quick response. I use the FAS-DPD method for CYA measurements. Is there a better CYA measurement method to get a better CYA as that is the only thing I can think of ... CYA higher than I am reading .... then I would need to drain some water to get the CYA back down.

You are losing me a little. Are you thinking higher CYA is the cause of your chlorine loss? It isn't.

 

[kenbob57]

Thanks. Your correct that high CYA is not causing my lose in Chlorine. So OCLT test was good. Will a solar cover during the day slow chlorine consumption? Will the solar cover cause other issue.