Hundreds of Black spots

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T

tclproductions

Bronze Supporter
May 20, 2017
64
Westlake village, CA
Hi !

I posted here a few years ago when my conditioner level was terrible and I had to deal with some yellow algae. I ended up chlorinating the Crud out of the pool that summer.

The recommendation was to dump water. In the fall season that year we had terrible fires in CA and my house almost burned to the ground. When I cleaned up my pool afterwards I dumped about half the water because I just sucked the ashes out of the pool that way. Using the Filter in Backwash mode.

Then we had an enormous rain season, just like this year. So I got calcium free , FREE, refill. Awesome!

My conditioner level was back to 50... and I was able to use "normal" amounts of pool chlorine and use the regular test kits.

Last year, using the solar cover, I got the pool to be about 95 degrees for 2 months. A giant hot tub, so much fun at night. But I noticed in July starting to get black spots all over. At first small, then bigger and more. By the end of august I had them everywhere. Brushing off with metal brush not very effective. I have seen those before years ago and they normally would go away in the winter time when the water goes to 45 degrees.

They did subside a little bit this year too but not enough. Now the water is back to 80 degrees. How the heck do I get rid of these black spots? It doesn't seem like shocking the pool kills them.

Thanks! - Just got my refill kit here so as soon as I get it I can make measurements. For now, using my regular test kit. Chlorine 5, Ph 7.5.
 
Post some pics and see if your spots look like the pics here...

www.troublefreepool.com

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.
www.troublefreepool.com www.troublefreepool.com
 
As the reference in Allen's post indicates do the smudge check. If smudging a sample does not turn green it's not black algae. When I've done this test using a snorkel I notice the green even when I scrap the sample off with a fingernail... also same effect on the bottom with a little vigorous scrubbing. Do exactly the full treatment including a week after at the high end of the FC range and it will be gone. Look for the first few dots and treat then for future outbreaks. If treated early it's way easier.
 
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Hi everybody - got my kit

So here are the specs:

FC: 4
CC: 0.5
CH: 875
TA: 150-160

here comes the big shock for me - CYA: 0

I was under the understanding that CYA never leaves your pool. Few years ago I was battling enormous 150+ levels, then I dumped a fair amount of water and let it refill with rain. Last year, I remember having 50 which is perfect. I have not filled the pool for 6 months with my water, CA rain took care of that for me. But now I am at 0 CYA which explains why my chlorine levels never hold much anymore.

How can my CYA just be gone?

I am also attaching a picture of the spots.
 

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tclproductions said:
How can my CYA just be gone?
Click to expand...

How is CYA Lost and Degrade in Pool Water?

High pool water temperatures will cause the chlorine to oxidize Cyanuric Acid. This tends to show in water temperatures of 90+ degrees. Every 10F increase in temperature results in roughly doubling the rate of degradation.

Chlorine breakdown in sunlight causes CYA degradation by hydroxyl radicals. This can cause a loss from 2 ppm per month to 10 ppm per month depending on the amount of sunlight the pool is exposed to.

In an area with 90+ pool water temperatures and extreme sunlight exposure 10+ ppm of CYA a month can be lost through degradation.
 
tclproductions said:
Hi everybody - got my kit

So here are the specs:

FC: 4
CC: 0.5
CH: 875
TA: 150-160

here comes the big shock for me - CYA: 0

I was under the understanding that CYA never leaves your pool. Few years ago I was battling enormous 150+ levels, then I dumped a fair amount of water and let it refill with rain. Last year, I remember having 50 which is perfect. I have not filled the pool for 6 months with my water, CA rain took care of that for me. But now I am at 0 CYA which explains why my chlorine levels never hold much anymore.

How can my CYA just be gone?

I am also attaching a picture of the spots.
Click to expand...


Wow! Yeah we had 95 degree pool water last year for months...now that makes sense
 
CYA of 40 is good to shoot for now. You may want to go to 50 during late summer when your temperatures rise.

The pool water is perfectly safe to swim in up to SLAM level for the CYA you have. No one will know there is even chlorine in the pool.
 

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I have done the smudge test and yes, it’s greenish. Some of the spots can be brushed off. But some cannot be brushed off with a metal brush and vigorous brushing.

whats my next step after I bring the CYA to 50? (And chlorine to a appropriate level). I have too many spots to manually brush on a daily basis. It’s a diving job.
 
If you have black algae I would keep your CYA around 40 until you solve that problem. Higher CYA will require maintaining higher FC level for a few weeks and will be more difficult.
 
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