FC/TC Equal; CYA 35 Green in winter- what now?

[Samanthawatts33]

I took over this pool about two years ago, and with your help I've been mostly successful *(Finally!)- do you think I'm missing something?

For the first 10-12 years only pucks were used. NEVER had a full/partial drain. Minimal water quality problems, at least that I know of. Only ever tested 'basic' chlorine/pH with cheap drop tests. Used same test kit for many years at a time.

Starting two years ago:
Year one, basically same as before- started having mustard algae issues periodically. A lot of difficulty maintaining pH levels.

Year two- found TFP. Started testing more often with a better quality kit. Switched to liquid chlorine. pH became fairly stable. Mustard algae never returned once I dedicated to TFP methods!

CYA- was never 'high'; testing range over past year has been 30-40. (I expected it to be very high- right?)

FC/TC- in the beginning there was an occasional variance (meaning CC was NOT 0), but it self corrected rather quickly. Within 3 months, FC/TC was consistently equal.
**I did miss the importance of the better TC/FC/CC test kit.

I just returned from being out of town for five weeks, found a green-ish pool when I got home. Weather had warmed above 70 for a couple days. I raised pH to 7.5, pouring acid above steps where growth was most abundant. Almost immediately the green growth was eradicated there, green hue to water gone- just cloudy at this point. Next day, I added 2 gal. bleach (per pool math using fresh test), this time pouring at 'other step' where there was growth. Now there is NO green, NO growth spots, just cloudy- I'd say the water appears 'thick' more than it is 'cloudy' if that makes any sense.

1. Continue SLAM? I'm concerned about getting FC down again in this cooler weather. Dogs drink from pool, can't prevent it no matter how hard we try.

2. Do you think I'm doing something wrong in the testing? Sure seems like CYA should be much higher- 12 years of (mostly) puck use (and shock 'bags') plus evaporation- never drained any of the water. (ie, where did all that stabilizer go?)

3. A lot of scale buildup at water line- suggested procedure? Can I drain just below the scale line, acid&scrub scale (scrubbing alone won't do), then drain the recommended 30% (due to 400-420 CH) after a few days of filtering to remove the particulates released?
**Would it be better to acid and scrub 2-4 tiles at time over the course of several months? (1-3x per week)

CURRENT TESTS:
FC/TC- 12
pH 7.2
TA 190
CH 420 (at 38 drops went purple, 39-41 blue-purple)
Yesterday CYA- 35
Water Temp 58

Anticipating mid-high 70s over the next week.

 

[Texas Splash]

Unfortunately, you appear to not only have some algae cloudiness, but also may be confused about the use of acid. Remember that acid is used to lower pH (and TA), and not designed to kill algae. To kill algae you must SLAM - period (bleach). That's the only way.
If your tests above are accurate, then your pH is perfect to start a SLAM. Increase FC immediately with regular bleach to your SLAM level of 16 (based on a rounded-up CYA of 40)

That is your #1 focus right now - SLAM. We'll address the high TA and questions about CH after you pass the SLAM. One thing at a time.

- - - Updated - - -

As for the FC/TC note above, just remember it this way..... You should only be concerned with FC (free chlorine) and CC (combined chlorine). Those two equal "TC". But we need to know the FC and CC. FC is the good chlorine from your bleach. CC is the trash/residual junk waiting to get oxidized by the sun. You are testing with a TF-100 or Taylor K-2006 correct? If so, then just load those two (FC & CC) separately for us in the future.

- - - Updated - - -

About your scale and CH. Your CH reading of 420 is fine. Many in the southwest have double that with no problem. But the pH and TA must be adjusted properly as well which is why I suggested just waiting until after your SLAM before we get into that stuff. We'll also give you some tips to try around the water line as well.

 

[Texas Splash]

Oh, and yes, if your pool was always fed tabs and bags-o-shock, we would expect the CYA to be through the roof. However if you are using your TF-100 or Taylor K-2006 to test (looking in the tube with the black dot) then you'll get an accurate reading. If you have questions about how to do the CYA test, let us know. It certainly is important. Having an accurate CYA is the foundation of pool maintenance, not to mention the SLAM.

 

[Samanthawatts33]

I know acid isn't supposed to kill algae- but I also knew I had to get pH right before I SLAMed. I was just amazed that it did kill it- instantly. Thought I'd include that detail in case my confusion was that I wasn't actually looking at algae-.

I am using the CYA test from the TF-100, I already had a complete test kit so I purchased those parts only. I will review the test instructions and make absolutely certain that I am doing it properly. Now that I wish I wasn't solely depending on my math skills (. 5FC -.5 TC= 0 CC sounded simple at the time), confirming my results sure would be nice- I was just too impatient to order online!

I did adjust the pool fill level last summer, probably too high. Is it possible that my pool has been dumping access water? I found some test results from last year- I had CYA of 80 (might have misread test) on 9/12 and CH of 600 on 9/21 (I'm confident of that reading). Yesterday, those numbers were 35 and 400. Since I started using exclusively liquid chlorine or bleach shortly before that time, is it possible that I have unwittingly replaced enough water to bring down these numbers?

Thanks so much!! I'll continue on with the SLAM for now, then address the unsightly water line.

 

[Texas Splash]

Glad you have the TF-100. You can't go wrong there. As for the pH and acid .. now I too understand. So that leaves us with the SLAM right? As long as you have no questions on the SLAM, increase your FC and you'll be on your way. Just make sure you follow all the instructions on that SLAM page (link below). Losing CYA and CH since winter? .... I suppose it's possible if you did indeed lose a significant amount of water. But you would've had to drain it yourself. No worries though. After the SLAM we can go over TA and CH adjustments easily. Right now we need to help you get rid of that algae and cloudiness. Just to be sure on CYA, here's a couple things to review:Testing Cyanuric Acid with the TF-100 - YouTube

Proper lighting is important for the CYA test. You want to test for CYA outside on a sunny day, but keep the skinny view tube in the shade. Taylor recommends standing in the sun with your back to the sun and the view tube in the shade of your body. Use the mixing bottle to combine/mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then mix again. Then, while holding the skinny tube with the black dot at waist level, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. Once it disappears, record the CYA reading. After the first test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate the CYA reading.

- - - Updated - - -

If you think your CYA is anything other than what you said before (35-40), then we will adjust your FC shock level according to the Pool School - Chlorine / CYA Chart. I really don't want to overwhelm you right now, so we'll just focus on the correct CYA validation, then making sure you have the correct FC shock level for that CYA from the chart.