I'm getting what looks like green algae this season

[nikon5400]

Don't know that the cause is. everything is within range

0003 doesn't change the color at all (it used to a little previous seasons and one drop of 0871 would clear it. but this time 0003 doesn't change the color at all it stays clear)

my cya according to my tests with 2 new 0013 is less than 35.

I shocked my pool 2 days ago bringing it up to 18

Right now my FC 4.5 and I have some green and brown (dead algae?) spots that can be wiped off by fingers.

I've been using BBB for a few seasons now, never had this issue. My CYA was very low when I opened this season and this was the first time when I had to raise it.
I believe my CYA was around 50 previous seasons because i used to keep higher FC levels and I wonder if I should keep it at around 50 to avoid this issue?
My CYA tube is about 5 seasons old. Should I get a new one?

Thanks

 

[pwrstrk]

From what I see you attempted a SLAM and stopped short with it. You have visible algae. To avoid algae you need to keep your FC in range for your CYA level.
I recommend that your read the SLAM Process and you have to follow it to the T.
Get a good reading on your CYA level. If it's low the better you will be to SLAM. After your SLAM is done then raise your CYA. ?

 

[nikon5400]

I just replied, not sure what happened to my post

here it is again (sorry if duplicate)

CC is 0.5 or lower;
You pass an OCLT (ie overnight FC loss test shows a loss of 1.0 ppm or less);
And the water is clear.

my cc is 0
my overnight loss has always been about .5. I don't think it's ever been 1
my water is clear

I add chlorine at night, bringing it up from 2 to 5, which is about half a bottle of 12.5% liquid.
My CYA is 30-35 according to my tests. I started using tabs now, trying to bring CYA up a bit since I had 0 problems when it was around 50.
The algae shows up all of a sudden and goes away without much effort. There's only one or two spots I had to brush a little and they are clear now.

It's not like I look at my pool and see algae right away. but if I spend time looking for it, I'll see it in a couple spots, like tile edges. But that algae goes away by touching it with a finger

Question - when I lose about 3ppm during 85-90 degrees day and no shade (and no tabs, just liquid chlorine added at night), is my CYA likely to be 30-35 or much higher?

 

[pwrstrk]

Ok. Do you have any visible algae ?
The 12.5% chlorine have you ever tested after the addition to confirm it raised your FC what it was supposed to ?
Your OCLT test, probably less than 1. That has to be for sure. I'd take my FC to a elevated level. Test 20-30 minutes after the addition of chlorine to see what the FC level is for sure. Then test in the morning before the sun comes up.

 

[pwrstrk]

You added to your post while I was posting.
Are you using the TF - 100 kit ? Your CYA level could be higher. Are you performing test correctly ?
How many hours of sun does the pool receive ? 2-3 ppm loss of FC is normal.

 

[pwrstrk]

Bottom line for me is if your getting algae no matter how slight, your FC isn't in range for your CYA level. That's why you have to have to know where the CYA level is so you can keep your FC in range for it. ?

 

[nikon5400]

I've used TF-100 kits for 5 seasons. All agents are fresh.
Pool is under sun all day, until may be 6pm or so.
I can only suspect my CYA is higher, but how else do I verify it? That's why I'm asking, is FC gong from 5 to 2 during the day typical for CYA 30-35 or higher?

 

[pwrstrk]

If your pool is in full sun all day with a CYA level of 30-35 you going to lose 3 ppm I would think if not more.
You stated at 50 ppm of CYA you had no problems.
One more thing. The 12.5% chlorine degrades quicker than say 8.25% bleach. I've used 12.5% and it was about a month old when I bought it. It didn't raise my FC the amount pool math said it would. It was 1-1.5 ppm off. Lower. It was more like 10%. The higher the chlorine precent the quicker it degrades.
You verify the CYA by getting a good test on it. If it's 35 I would be targeting my FC levels to a CYA level of 40.

 

[nikon5400]

I see the dot until it gets to 30-35. I've used this same tube for last 5 years

 

[pwrstrk]

If your still seeing slight algae I would SLAM the pool until the three criteria are passed.
1 water is crystal clear
2 CC of 0.5 or less.
3 pass the OCLT.
Then I would take the CYA level to 40-50, and keep the FC in range for the CYA level.
At least do an OCLT confirm organics or not.
It's your call. ?