Am I doing something wrong?

[LHK]

Hello all,

This is my second summer with a pool and my first summer using the TFP method. I did a big SLAM earlier in the year that took a couple weeks, but then had the pool sparkling clear. Then we had a big storm that left enough debris in the poll that it took me 2 days to clean up, algae flared up again, spent another week SLAMing. Between those 2 SLAMs I know that I have no algae in any hidden places and I've done a deep clean of the sand filter (and maybe even broke a couple of the laterals doing it, but that's another post...). It may be important to note that we also have about 10 long wrinkles in the liner from last summer when we moved in and the drainage system around the pool failed and flooded the space around the pool. When the plumber cleared it, the water drained too quickly for us to smooth out the liner. And we just a had a small hole on one of those wrinkles that I repaired myself a week or so ago a few days after it occurred. Ok, now on to the important part...

Now I keep going through these cycles where dirt/alage accumulates, mostly along the wrinkles, but there have been some small patches on the flat parts. Then I spend a few days caring for the pool as usual, making sure I run the dolphin to clean it up, and mentally preparing myself for a SLAM. Then I SLAM, which takes 2-3 days depending on how long I deliberated in the previous phase. I wait for all criteria to be met before stopping the SLAM. But a few days later it starts again with the dirt/algae along the wrinkles. I'm essentially "shocking" it once every 1-2 weeks, but I thought that shouldn't be necessary with the TFP method.

The water is always very clear, never cloudy. My recommended Cl level is 3-7. When I check at the end of the day, it's always 3-5, never drops below 3. I add enough liquid Cl to bring it back up to 7.

FC - 4.5 this morning after about 2 hours of sun ( I don't usually check it in the morning, but I wasn't surprised that it wasn't higher)
CC= 0
pH = 8.0 (I'm working on getting this back down, but it does creep up quickly)
TA = 9
CYA = 40
water is crystal clear

Thanks for your help,
Laura

 

[kellyfair]

If you are absolutely sure your CYA is 40, then you need at keep your FC between 5-7. 3 is the absolute minimum, not the target, and having it that low is leaving you no wiggle room at all. You could even shoot for 8.

If there is a chance your CYA is higher, then your FC is definitely not high enough. How do you do the CYA test?

 

[LHK]

Thanks, kellyfair. My CYA was actually measured at 35 with my Taylor test kit, but I was told to round up to 40. I tested a few weeks into the summer when I go the kit. I haven't added any CYA, so if anything it's a bit lower than 35 now. Probably a good idea for me to check it again since I lost a couple inches over the few days to took me to patch the hole now that I think about it...

So you think I just need to keep the Cl higher to stop the need for frequent SLAMing?

 

[kellyfair]

Can you tell us step-by-step how you do the CYA test? Only in full sun, with your back to the sun?

 

[LHK]

I don't remember the specifics of my position to the sun when I did the test, but I remember following the directions very closely and then seeing a detailed post here on how to do it and thinking, "yep, I did it right." I remember giving it a quick glance as I was filling the column rather than staring at it. I'll retest it later today and see what I get.

 

[LHK]

Ok, so I reviewed the proper way to do a CYA test (from this site). I did the test with my back to the sun, holding the sample at waist level. I thought I was supposed to just glance at it, but review of the instructions say the dot should not be visible even after I stare at if for a few seconds. I did the test twice with the same sample (Instructions say I can do that). The first time it was right at the 30 ppm mark when I lost the dot. The second time it was just below the 30 ppm mark, but above the 9 ml mark (which is halfway between the 30 and 40 ppm mark). I took pictures as I went along (which I can post later), but even in review of those, I can still see the dot a tiny bit when I stopped short of 30 ppm, so I really do think it's 30.

If that's the case, maintaining Cl as I have been should be enough, right? It's never below 3 at the end of the day.

I tested again this afternoon:
FC= 4.0 (so I lost 0.5 over the course of a partly cloudy day)
CC= 0
pH= 7.6

 

[CraigChing]

I would err on the side of a higher FC level, particularly since you’re getting algae. The numbers we get from testing are really abstractions that aid us in pool care. The reality is what we’re really after, clean clear pools. With a CYA of 30, if you want to go with that, has a target of 5-7. I’d aim for 7 and see if that gives better results rather than trying to low ball your target.

 

[LHK]

I've been adding chlorine at night to bring it up to 7 - should I start aiming to bring it up to 8 or 9?

 

[kellyfair]

No, I would not stare, I would glance. And just fill it to the next line (20, 30, etc.) rather than stopping incrementally.

As I mentioned earlier and Craig did too, you should strive for a target that is higher than the minimum. So, 7 or 8, and see if that helps your pool stay clear (after you SLAM to get it clear if it isn’t already).

 

[LHK]

Update - the sun is off the pool, so I went out to check the FC and "top it off" for the night. FC was 4, which is consistent with where it's been for my end of the day check. (Note: In my original post I meant to say that I *was* surprised that the FC wasn't higher than 4.5.) Which got me thinking...If I only lost 0.5 ppm over 9 hours of a partly cloudy day (10:30 am - 7:30 pm) it doesn't make sense that I would have lost 2.5 ppm between the 12 hours prior... So I think somehow I'm not really getting to 7 at night. Maybe I'm not getting the liquid Cl up to the right line on my container or something, idk. I'm pretty sure I have the volume right.

I added enough Cl to bring it up to 8 tonight just in case I have been getting to 7 and I'm missing another piece of this puzzle. I'll check it in a bit to make sure I made it to the target.

Laura