Readings took a turn today - FC holds but CYA is gone

[Nebuchadnezzar]

Hey everyone. I just wanted to first say thanks. I discovered this site last year and as a result spent way less $ on my pool and got better results.

Anyway, I opened the pool about a week ago. Over the winter I didn't bother covering it because of the warm temps in the south. So at opening I had a green pool. Testing the water then I found I still had a CYA of 50, which I was happy about. Last year it took a long time to get my pool started mostly due to my battles with keeping the FC high with low CYA (adding it takes a LONG time) and I was hoping to avoid that this year.

Opening day results: FC 0 CC 0 pH 8+ (deep purple on the Taylor) TA 60 CH 130 CYA 50

So after a week of pouring gallons and gallons of bleach into the pool, trying to keep the FC above 15ppm (I have gunite so I'm not worried about super high FC levels), running the pool 24/7, I tested this morning:

FC 3.5 CC 1.0 pH 7.4 TA 70 CH 120 CYA 0!

Since the last time I added bleach was yesterday AM I figured this meant I'd cleared the hurdle of maintaining FC levels and could start working on other stuff - but my CYA is gone. I guess all the algae in the pool that I've been stirring up by raking and brushing ate it all. I would drain and refill but city water prices have gotten ridiculous to the point where dumping in bleach seems cheaper. That and my main drain is plugged.

I figured that I should get the stabilizer levels up so I put some pucks in my skimmer. Not sure if they're di- or trichlor and can't remember where to find that info on here. Of course THEN I had to refresh my reading on what to do if you have no stabilizer and now I don't know what to do b/c that seems like it was the wrong thing to do. My pool is cloudy, but blue. I can't see the bottom so it's tough to judge if I've gotten all the junk off the floor. I think I'll brush the walls while I wait for a reply and then search for how to tell what kind of tabs are what so I can update my spreadsheet.

My pool stats are in my sig. I have the Taylor K2006 kit and I generally use the powder test for FC. I do have an OTO kit somewhere if that's OK to use sometimes. The Taylor kit is more fun though, heh.

[Watermom]

Having a cloudy pool, (plus that CC reading of 1) means that you aren't done yet. A lot of the cloudiness is most likely dead algae, but you need to continue to keep the chlorine high (with bleach, not pucks) a little longer. Have you tried to overnight test? Test your chlorine level at sundown and then within two hours of sunrise the next morning. If you lose more than ppm of chlorine overnight, then you need to maintain the chlorine at shock levels. It is best to add bleach in the evenings rather than in the mornings, by the way, so all of it can go towards sanitizing the pool/killing algae instead of having part of it lost to the sun.

Keep running your pump and filter 24/7 while you are working to clear the pool. Watch your filter pressure and backwash whenever the pressure rises 8-10psi over clean filter pressure.

Also, those pucks are trichlor. You can't shock with trichlor so save them until you are finished clearing the pool and then you can use them. Hope this helps. Glad to see you back around the forum this year!
I can't explain why the CYA dropped from 50 to 0 in that short of a time period. Are you sure it is not a testing error?

[Nebuchadnezzar]

Having a cloudy pool, (plus that CC reading of 1) means that you aren't done yet. A lot of the cloudiness is most likely dead algae, but you need to continue to keep the chlorine high (with bleach, not pucks) a little longer. Have you tried to overnight test? Test your chlorine level at sundown and then within two hours of sunrise the next morning. If you lose more than ppm of chlorine overnight, then you need to maintain the chlorine at shock levels. It is best to add bleach in the evenings rather than in the mornings, by the way, so all of it can go towards sanitizing the pool/killing algae instead of having part of it lost to the sun.

Keep running your pump and filter 24/7 while you are working to clear the pool. Watch your filter pressure and backwash whenever the pressure rises 8-10psi over clean filter pressure.

Also, those pucks are trichlor. You can't shock with trichlor so save them until you are finished clearing the pool and then you can use them. Hope this helps. Glad to see you back around the forum this year!
I can't explain why they CYA dropped from 50 to 0 in that short of a time period. Are you sure it is a testing error?

Thanks for the reply. I have actually kept track of my results this past week and I do generally test in the mornings and evenings. I am not always good about adding Cl at night as I'm usually on my way to work but now it's time to get real so I'll figure something out. I have made some good progress as at least now I am having FC when I test in the mornings. However compared to the previous evening I've always lost FC. I'm assuming btw that you meant that losing even 1 ppm of FC overnight was bad.

Brushing the sides this morning seems to have helped a lot as I had to backwash again tonight, making twice in one day. My gauge has the little dial that lets you set the starting pressure so you can see where you need to backwash, very helpful feature.

Tonight's results: FC 7.5 CC 1.5 pH 7.2 CYA 0

Unfortunately I am out of bleach and can't get any more until tomorrow - I only had one big jug left, which works out to 3ppm in my pool. But I will take the trichlor out in the AM and stick with using bleach until the water has cleared up. Trichlor is no good for shocking, obviously, but I just want to keep the FC as high as possible until I can get more bleach. The pucks are old anyway.

I retested the CYA and it still came up 0. I might have made an error in testing last week but I'm positive I read the results correctly - I had such problems with stabilizer last year that I went through a whole 2oz bottle of reagent thinking I was doing something wrong until finally I got cloudy test water! My theory is that, since the level of algae in my pool at opening was pretty low (light green as opposed to dark, dark green), that the stabilizer was OK until I started stirring things up by raking and brushing, releasing all the bacteria into the water that had been trapped under the layers of pine straw and leaves, and they ate the CYA.

I'll have to read up on CC as all I know about it is that it reads the level of chlorine bound to "stuff" that has not been filtered out yet so it indicates that there is still junk to clean up in the pool ... yeah need to read more on that.

[Watermom]

As long as you only lose 1ppm of chlorine overnight, that is fine.

Combined chlorine is what forms when free chlorine combines with ammonia, nitrogen, and other "pollution" in your water and loses its ability to sanitize the water and kill viruses and bacteria. (A lot of the "pollution" is from sweat, urine, algae, etc.) It is typically what you are smelling when "a pool smells like chlorine." You are smelling the combined chlorine. Ideally, you want the CC (combined chlorine) level to be 0, but up to 0.5 is generally not a problem. The way to rid the pool of CC is to shock it. That is not a very technical explanation, but hopefully it will help clarify it for you somewhat.