Chemical levels

[dcraven5]

Hi All,
I'm now a 2nd year pool owner but a newbie to TFP. I am armed with a Taylor K2006c test kit, a case of liquid chlorine and the Poolmath app. The pool looks good but I feel like the chlorine levels are dripping quickly. 11 ppm yesterday, 5.5 ppm today. Is this normal? Does it have something to do with my specific chemistry? Attached is a screenshot of recent activity from the Poolmath app. TIA for any advice and let me know if I should include additional information.

Doug

 

[HermanTX]

Welcome to TFP.
Thanks for testing with a recommended test kit.
Your additions are about spot on. According to PM, 1 gal of 12.5% LC will raise FC by 6.8ppm which when added to 4.4 is on mark for the 11ppm you recorded after the addition. So that looks good.
You tested CYA at 60ppm so assuming that is correct, it shows you loss 5.5ppm of FC over 20 hours which seems high especially if that included night time. That leads to thinking you may have something lurking. Suggest you add more LC today.
Then plan to do a Overnight Chlorine Loss Test tonight. This will isolate the effects of UV to determine if something is lucking.
Also you did not put in your location but your pool water temp was 79 degrees so I assume you are in mid or northern USA. Please update your location because that influences what we may know about that area.

 

[dcraven5]

Welcome to TFP.
Thanks for testing with a recommended test kit.
Your additions are about spot on. According to PM, 1 gal of 12.5% LC will raise FC by 6.8ppm which when added to 4.4 is on mark for the 11ppm you recorded after the addition. So that looks good.
You tested CYA at 60ppm so assuming that is correct, it shows you loss 5.5ppm of FC over 20 hours which seems high especially if that included night time. That leads to thinking you may have something lurking. Suggest you add more LC today.
Then plan to do a Overnight Chlorine Loss Test tonight. This will isolate the effects of UV to determine if something is lucking.
Also you did not put in your location but your pool water temp was 79 degrees so I assume you are in mid or northern USA. Please update your location because that influences what we may know about that area.

Thanks for the quick reply. I have added my details to my signature. I will test again tonight after the sun sets to see how much it may drop during the day. Afterwards, I will add the chlorine and test again after it circulates and then again in the am. I will reply back with results tomorrow.
Thanks for your help!

 

[pjt]

For the FC test, use a 10 ml sample so each drop is 0.5 FC. Saves time and reagents.

 

[SJPoe]

Also - try to be consistent with your testing process.
Sample from the same place in the pool, at the same time, in the same way.
If you have an SWG - make sure you're not sampling in the direct outwash from a return...you'll possible read higher than the 'overall' level
If you use Liquid Chlorine, make sure you're allowing ample time for it to mix/disperse after dosing, or measure before dosing each time etc.

Other things that can significantly impact the FC - is the pool covered - was is sunny, cloudy, poured with rain etc.

Also, keep in mind the margin of error - if your previous day number was -0.5, and your today number was +0.5, then your loss is 10.5 -> 6 - which is 4ppm, which isn't out of the realm of normal for a pool in direct sunlight on a nice day at 60 CYA...

 

[dcraven5]

We are in direct sunlight and do not have a cover, so that is definitely contributing to some of the loss. Below are the latest test results. Chlorine dropped 1.9 through the day and 0.8 overnight. Would it help to change the sand in the filter? The previous homeowner thinks it's been about 5 years.

 

[HermanTX]

We are in direct sunlight and do not have a cover, so that is definitely contributing to some of the loss. Below are the latest test results. Chlorine dropped 1.9 through the day and 0.8 overnight. Would it help to change the sand in the filter? The previous homeowner thinks it's been about 5 years. View attachment 576540

Thanks - so the Overnight Chlorine Loss Test was less than 1ppm based on your info. So that is fine. It may be just the direct UV and you only loss 2ppm during the day.

Do you know if the sand filter has been backwashed? Here is good article on sand filters - Sand Filter Use and Care - Further Reading

 

[SJPoe]

We are in direct sunlight and do not have a cover, so that is definitely contributing to some of the loss. Below are the latest test results. Chlorine dropped 1.9 through the day and 0.8 overnight. Would it help to change the sand in the filter? The previous homeowner thinks it's been about 5 years.

3ppm in 24 hours in an uncovered pool isn't unusual. 0.8 overnight is within the usual "you're clear" level too. How does the water look, and the CC numbers? If it's crystal clear, and the CC is less than 1, then I'd suggest doing a complete set of tests (CYA, TA, CH, PH) and posting those and we can tweak accordingly. If the pool is cloudy, then maybe the filter needs looking at. Backwashing as suggested probably isn't a bad idea...

 

[dcraven5]

Thanks for your help everyone. The pool is clear, no cloudiness at all. Backwash performed and n full set of tests run, results below. Looks like chlorine loss is staying consistent and will be something I need to get used to. Maybe a SWG is in the future!

 

[HermanTX]

Thanks for your help everyone. The pool is clear, no cloudiness at all. Backwash performed and n full set of tests run, results below. Looks like chlorine loss is staying consistent and will be something I need to get used to. Maybe a SWG is in the future!

View attachment 576953

That is great. Now you can work on lowering TA if that is your desire. Add MA to lower pH to 7.4, then areate to raise pH. Repeat. It may take weeks to lower TA to 80-90. Just a suggestion. The goal is to stabilize pH - if it is rising quickly (somewhat indicated by the positive CSI calculated number).
Not sure if you are aware, but on the Home Screen of PM app, you can click on the CSI icon, then change TA to a lower number and it will calculate a new CSI. You can change multiple components. It will not save the changes, but the goal is to show you if you make changes to the variables what effect they have on CSI. For example, rising water temperatures will cause CSI to become more positive. Lower pH will drive CSI more negative.