Magical Chlorine Appearing Out of Nowhere

[chadly]

I'm so confused.

I'm a new pool owner and this is my first foray into all of this. I posted earlier about how I was SLAMing the pool. Well, I tried to do the OCLT last night. After the sun went down, I measured FC of 12.5. I turned the SWG off (set the Aquapure to 0% in the iAqualink app) and went to sleep.

I woke up before the sun started hitting the pool and measured again and got a reading of 15 ppm.

How is that possible? I'm obviously doing something wrong but I can't figure out what. The FAS/DPD test is pretty simple to do. I don't think I'm doing it wrong. Is the salt generator not really off at 0%? Is there another way to really turn it off? Am I being visited by the Chlorine Leprechaun in the middle of the night?

The only thing I added to the pool last night was a little bit of muriatic acid to balance the pH. But, I did that an hour before I did the FAS/DPD test before I went to bed.

 

[Rancho Cost-a-Lotta]

Am I being visited by the Chlorine Leprechaun in the middle of the night?

Well, you do you live in NOLA, so anything's possible.

 

[Arizonarob]

Chad do you have a speedstir?

 

[mknauss]

Most likely not complete circulation prior to your test last night.

Do another tonight. Brush the pool vigorously prior to testing with the pump at 2500 rpm or higher. Wait an hour and test the FC.

Run the pump all night at at least 1200 rpm. In the morning, take the sample from the same spot you took the one from the evening before.

 

[duraleigh]

During your FAS/DPD test, always hold the R-870 bottle vertical and always let the drops FALL off the tip......don't force them off.

Additionally, always make sure that your last drop makes no difference whatsoever to the color of the sample and then subtract that last drop.

You may be doing that already but it insures maximum precision on the test.

 

[Richard320]

My guess: Your wife is so sick of hearing you talk about pool chemistry that she snuck out and dumped another jug in just to confound you.

 

[chadly]

Thanks for the tips. I'll try again tonight and measure in the same spot.

 

[Wobblerlorri]

Be sure you rinse and clean your sample tubes thoroughly between uses, too. Another thing you should do is do NOT take your water sample from the surface of the water. Keep your bottle closed and plunge it about 18" deep ( conveniently the approximate length of your arm up to the elbow), then remove the lid and take your sample. Be sure to rinse your sample bottle between uses, too.

Techniques I learned when I was a water microbiologist.

 

[Steve_in_C]

Kinda reminds me of the guy at the country store who was bragging about how many eggs were laid by his hens. Eventually the bragging escalated to more than 1 egg per day per hen. This was all due to the fact that one of the other guys at the store was sneaking in to the chicken coop and adding eggs to the nests.

 

[Bama Rambler]

This was all due to the fact that one of the other guys at the store was sneaking in to the chicken coop and adding eggs to the nests.

And this kinda reminds me of the time we added gasoline to a guys new VW Beetle. Started at about a cup a day and increased to over a pint a day over time so it wound up actually making gas!

As for your test results. If this was the sequence of events,

1) After the sun went down, I measured FC of 12.5. 2) I turned the SWG off (set the Aquapure to 0% in the iAqualink app) and 3) went to sleep.

you did the test and then shut the swg off, you most likely had some FC being produced that hadn't fully mixed and that affected the outcome.

As mentioned above, shut the swg off and wait 30 minutes to an hour with the pump running and then run the FC test.