Black spots - algae?

[poollizard]

I'm getting ready to drain and refill my pool in order to reduce the CYA and CH. I also have three black spot areas that I can't brush out, I was wondering how to remove the spots after all the water is drained.

Here are my test results from yesterday:

FC = 8
CC = .5
pH = 7.5
TA = 150
CH = 600
CYA = 240

 

[RobbieH]

My guess is black algae, can you post a picture. Removal of black algae is difficult. I use a wire brush. You should be able to scrape some off with a fingernail or knife, then squish it to see if it turns a dark green to ensure it is black algae. If you are draining, I would scrub with a wire brush then spray with a water/bleach solution.

 

[poollizard]

I do have a picture of one of the spots. This was taken this morning, through the water. It's not a very good picture. I also have a lot of scale. The other blotches are clear places in the scale.

 

[poollizard]

I'm getting ready to pump, any advice?

 

[RobbieH]

Looks like black algae. Wire brush. A small one will be more effective.

 

[poollizard]

See the white blotches? What is that? Is that calcium scale buildup? They feel smooth to the touch.

 

[RobbieH]

It could be. I'll let someone with experience with scaling give you advise.

 

[poollizard]

The more I look at it, the more I think it is the paint coming off. I can remember this whitish look getting worse and worse over the last 5 to 9 years. It could be scale I suppose, but when I run my finger over it the whitish ares are smooth, and then the other areas are kind of rough, like a pool bottom is supposed to be. There are no cracks or chipping any where on the surface. I am really beginning to think it's just that the paint has come off.

Any other opinions?

 

[poollizard]

After refilling my pool, can I use the SLAM method to get it rebalanced? Or is there another recommended procedure?


Oh yea, what is "shock level", referred to in the SLAMing procedure.
http://tinyurl.com/lzrlk2b

 

[danacc]

Was the pool painted?

Calcium scale usually feels rough. But if the pool had white plaster, some of the smooth areas could be places that don't have scale. I can't tell from the pictures.


Once you refill, you can adjust your water balance to prepare for a SLAM and then start it. Did you validate that you have black algae?


Edited to add: Chlorine level for the SLAM can be found here: pool-school/chlorine_cya_chart_shock.

 

[Jeetyet]

"Shock Level" is an increase from the normal level of FC that is designed to effectively kill any organics in your water while minimizing the risk of damage to your pool or plumbing. During the SLAM process FC is raised to shock level and maintained as closely as possible until you can pass an Overnight Chlorine Loss Test. Afterwards, the higher level is allowed to drop back into the normal maintenance range.

 

[poollizard]

Was the pool painted?

I don't have any details of the original construction of the pool. But I do believe it was painted.

Calcium scale usually feels rough. But if the pool had white plaster, some of the smooth areas could be places that don't have scale. I can't tell from the pictures.

In those areas where the paint is gone it feels smooth, and the color is either white or light gray.


Once you refill, you can adjust your water balance to prepare for a SLAM and then start it. Did you validate that you have black algae?

Do you mean to follow the SLAMing procedure after the refill?

I believe it is black algae. I need to finish draining in the morning and then attack the black algae.


Edited to add: Chlorine level for the SLAM can be found here: pool-school/chlorine_cya_chart_shock.

Thank you!!!

 

[poollizard]

"Shock Level" is an increase from the normal level of FC that is designed to effectively kill any organics in your water while minimizing the risk of damage to your pool or plumbing. During the SLAM process FC is raised to shock level and maintained as closely as possible until you can pass an Overnight Chlorine Loss Test. Afterwards, the higher level is allowed to drop back into the normal maintenance range.

Thank you for the explanation.

 

[poollizard]

Well, I got the black algae off, refill in progress.

It's obvious to me now that the pool surface needs repainting. I am going to tackle that job later this year or in the spring. Sometime when the weather is more suitable. Right now we are still having 100 degree temps. Ugh!!