Newbie Fighting Algea

[deichb]

Hello,
We are new pool owners and had cloudy water for a while. Found that SWG was set on low output mode contributing to very little chlorine. We started the slam process and have carried a high FC (13+) for three days. Cloudiness has diminished and pool vac is picking up white scale deposits. My daughter and wife used the pool today and I tested the water immediately after. FC dropped to .5 just after one swim session. What am I missing?

 

[HermanTX]

Welcome to TFP.
Please read Pool Care Basics for general information about pool ownership.
Are you following the SLAM Process?
You still have algae which is why your FC dropped drastically.
Please provide test results for your CYA in addition to FC.
The SLAM process needs to be followed and only stop it when all 3 criteria are met. It is not a one time dump and stop process.
Also, do you have a proper test kit. See the recommended test kits
Test Kits Compared

 

[deichb]

Hi,
I am currently in the SLAM process. I thought I was complete as my FC was stagnate at 13.8 and my CC was near .5. I tested this morning after adding 2 gallons of chlorine last night. FC spiked to 8.5 and CC is a smidge over .5 but less than 1 (testing using 10ml of water, thus 1 drop equals .5). 1 drop had a faint pink to it. We are using the Taylor K-2006 test kit. We did have to purchase some reagents separately to complete the CC testing. It sounds like I am close but not quite there. As a first time pool owner, I am unsure what to expect in regards to timing. Thanks!

 

[HermanTX]

Using the K-2006 kit the FC and CC test are definitive numbers.
If it takes 1 drop on the CC test to make the sample colorless then that is 0.5ppm, if 2 drop then that is 1ppm and is a failed test on the SLAM criteria

I do not understand why you are testing CYA daily and also why the CYA changes daily. Are you using the K-2006 kit for the CYA test? You should read CYA in decade numbers only - 30, 40, 50, etc.

At the beginning of a SLAM, measure CYA and that should stay constant throughout the SLAM because CYA is only added via use of stabilizer or by stabilized chlorine pucks.

Also, the FC level for a SLAM is 40% of the CYA number. So if the CYA is 60, then the SLAM FC level is 24ppm. That FC level should be Maintained (the M in SLAM) throughout each day the best you can by testing every 2-4 hours.
The more you test and top up the FC the quicker the SLAM will go.

Also there are 3 criteria for a SLAM to end
a CC of 0.5 or lower
Pass the Overnight Chlorine Loss Test with a 1ppm or less difference - it appears this has not been done
Pool water is crystal clear with no visible algae

Timing on a SLAM varies by pool size, the amount of algae at the start and how well one "maintains" the SLAM level FC.