Help from the experts please? Black algae vs replaster?

grguy

Member
Aug 15, 2012
6
First let me preface this by saying that I suck at pool work... I've been trying and last year I did well keeping up with levels. This year is a different story.
The electrical conduit that runs out to the pool rotted away - The upper part of the cartridge filter cracked open - Then the lower part let loose - bearings in the main pump seized - the SWG union cracked - the flexible pipe to the polaris pump sprung a leak. I know this sounds like a sob story and maybe it is but there were extended times of not being able to run the system to keep things stable.
I installed the swg 2 years ago and things went well then...
So now the part where I need help. We've developed what I believe to be black algae along mostly the sides of the pool, especially on the north side.
My wife, being proactive, called plastering contractors to get bids and we did. But I suspect when you call a plastering company, all they think about is replastering not necessarily fixing the issue. We will also need to replace the tiles on the upper edge as they are letting loose (and they're dated)
I may be wrong (and I have zero experience) but would an drain and acid wash be in order? The plastering company I talked to said it would make the plaster too rough and uncomfortable. But it's almost exclusively on the sides of the pool.
The pool was built the the early 80's and I have no idea anything done since then. After this, I promised to hire a pool guy to maintain the pool, but between just us girls the may last only one season before my pride sets in and take it over again :)
Thank you all, gurus, for your opinions in advance here.
 

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Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,945
NW Ohio
First thing's first: have you brushed at it without result? Generally with an algae issue like you show in the photos I wouldn't assume that it's black algae until you have successfully completed the SLAM Process, including daily brushing, and it remains despite clear water and regular brushing.
 

grguy

Member
Aug 15, 2012
6
Thanks Donldson
We had done the brushing thing to the walls with a nylon brush and a wire brush. Around July to mid September I had SLAMMED it and was stable for that while. Was never able to clear the black from the walls.
Then things started breaking again...
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
10,535
Northern NJ
Have you read...


Have you done...

gently scrape a sample of the suspected black algae with your fingernail and then smudge it on plain white paper. If the smudge scrapes off and is a greenish color, then it’s black algae.
 

Etchase

Active member
May 22, 2019
28
Hawaii
I’ve had some success using a pressure washer to knock down black algae, followed by high CL levels and brushing for a few days. It has always grown back usually in the same areas, but usually it takes over a year, and if you catch it early enough, just brushing over a small outbreak is enough.
 

grguy

Member
Aug 15, 2012
6
Thank you all for your input. I tried the fingernail scratch test and rubbed it on paper and got a "barely green smudge". I took some additional pics here.
I guess the question still is: Does this symptom require replastering the entire pool or will a super SLAM or acid wash clear it up? I get conflicting cues from sources.
We still will have the tile replaced either way. By the way, is there a difference between pool tile and tile that can be bought from a tile store (like Floors and Decor)?
Again, Thank you in advance for your knowledgable help! Mark
 

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Etchase

Active member
May 22, 2019
28
Hawaii
You can manage it with a drain and pressure wash. I found chlorine soaked towels stuck to the walls better then an acid wash, but others have had success with an acid wash. Slams aren’t effective at all, unless you actually brush the algae aggressively and frequently. Several times a day can be effective. I would choose the drain and clean if it was me, if water is cheap and your ground water level is low. I have no idea if my experience is representative or not.
 

Etchase

Active member
May 22, 2019
28
Hawaii
Pool tile is different then regular tile and usually quite a bit more expensive. I think it has something to do with how much water the tile absorbs when submersed.