Black algae & old PebbleTec finish. Remodel and refinish, or savable?

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Kisiel92

Member
Jul 2, 2022
9
Riverside, CA
Pool Size
17250
Surface
Plaster
Chlorine
Salt Water Generator
Hi all,

We have a saltwater pool with a longstanding black algae problem, which was already established when the home was purchased. There are entire sections of the PebbleTec which appear black in color which a nylon brush does not touch, but a stainless steel brush works on.

The PebbleTec is what was originally installed with the pool ~20 year ago, so wondering with how extensive the problem is if it's even worth investing and time and effort in tackling it or refinishing/remodeling the pool. There are crevices between the rocks at the waterline which also seem impossible to scrub even with the finest wire brushes, which we'll get rid of for sure with a remodel to make pool care less of a pain.

Most recent TF-100 test results:
FC 2.0 [currently increasing pump runtime from 5 to 8 hours]
CC 0-0.5 (pink from DPD testing is very faint, so guessing close to 0)
pH 7.7
TA 50
CH 475
CYA 65
Salt 3000
Water Temp 68F

Thanks in advance for your help!
 

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If you were already planning a renovation, you could do that.

Your chlorine is incredibly low so it’s not helping the situation. A slam is in order if you want to tackle the algae.

FC/CYA Levels
SLAM Process
 
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Kisiel92 said:
Hi all,

We have a saltwater pool with a longstanding black algae problem, which was already established when the home was purchased. There are entire sections of the PebbleTec which appear black in color which a nylon brush does not touch, but a stainless steel brush works on.

The PebbleTec is what was originally installed with the pool ~20 year ago, so wondering with how extensive the problem is if it's even worth investing and time and effort in tackling it or refinishing/remodeling the pool. There are crevices between the rocks at the waterline which also seem impossible to scrub even with the finest wire brushes, which we'll get rid of for sure with a remodel to make pool care less of a pain.

Most recent TF-100 test results:
FC 2.0 [currently increasing pump runtime from 5 to 8 hours]
CC 0-0.5 (pink from DPD testing is very faint, so guessing close to 0)
pH 7.7
TA 50
CH 475
CYA 65
Salt 3000
Water Temp 68F

Thanks in advance for your help!.
Click to expand...

If it brushes off easily, then more likely algae than copper staining (the other possibility). You should increase the chlorine to a more appropriate level and that will help. You can also try the SLAM process as it may not be black algae if it brushes off.

Here’s the instructions:
www.troublefreepool.com

SLAM - Shock Level and Maintain

We’ve all had to deal with a green pool. Clear algae from your pool with a SLAM! Read here to use shock level and maintain to clear your pool.
www.troublefreepool.com www.troublefreepool.com
 
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While checking around the house, have you seen any algaecides or other additives containing copper? How about a Pool RX in the skimmer? Is there any bluish discoloration of the filter grids? These would all be evidence of copper staining. Black algae does not usually cover such large areas.
 
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Thanks for the quick response all. I found a half empty bottle of algaecide containing 13% copper sulfate. Placed an order for dry acid on Amazon which will arrive tomorrow to test on the black residue. If it reacts, what's the process look like for dealing with metal stains?

Is it something like this?:
1) Close pool heater valves
2) Add tons of dry acid
3) Use a product like Curator or similar to sequester dissolved metals
 
Kisiel92 said:
Thanks for the quick response all. I found a half empty bottle of algaecide containing 13% copper sulfate. Placed an order for dry acid on Amazon which will arrive tomorrow to test on the black residue. If it reacts, what's the process look like for dealing with metal stains?

Is it something like this?:
1) Close pool heater valves
2) Add tons of dry acid
3) Use a product like Curator or similar to sequester dissolved metals
Click to expand...
You dont want to use dry acid especially with a SWG. It’ll wreck it. Only use muriatic acid if you need acid.

You can get a Jacks stain ID kit and confirm before doing anything.
 
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Thanks, that's really great info to know! I still think I'm going to use a small amount of dry acid since it's easier to test in a sock directly against the stain than muriatic acid. 5 lbs of the dry acid is $8 whereas the test is $15!

After reading about copper stains the last hour, I understand why the #1 piece of algae advice seems to be to under no circumstances use copper-based products to try to solve the problem quickly. If confirmed to be copper by the dry acid test, it seems like draining and acid washing might be the most economic option?
 
Yes, I did.

However, if I understood it correctly, it suggest that the dry acid (or muriatic acid in my case due to the SWG) reacts with the copper, resolublizing it, and then adding the Purple Stuff (for a saltwater pool) + maintaining the sequestrant level weekly. Would long-term use of a product like CuLator Ultra 4.0 remove the sequestered copper, or is it considered ineffective and draining / replacing the water is the only effective way to remove heavy metals?
 

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From the article.
Copper stain treatment does not remove the copper from your water, it only removes the solid copper stain from the wall by making it dissolve back into solution. So you still have copper in your water.

Sulfamic acid ([NH2]HSO3) is normally used to remove copper stains. Although it is extremely effective at lifting stains, sulfamic acid drastically affects water chemistry.[9] You find Sulfamic acid in Jacks Magic #2 Copper and Scale Stuff.

You then drain the pool and refill. CuLator is a scam. There is not enough resin in that thing to capture any appreciable amount of metal. If it catches any at all.
 
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The dry acid came in today and I tested it alongside one of the blackened sides, but it was difficult to tell if there was a reaction or not.

Decided to go ahead and order the Stain ID kit which i hope will be more conclusive sometime next week
 
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