Newbie and hit with black algae!

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aru_25

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Sep 6, 2013
12
San Diego, CA
We just purchased a house with a pool. Everything looked good with the pool during inspection when we purchased the house. We hired a pool guy to show us clean up and maintenance. After 3 weekly cleaning sessions, he left us a note saying that he can't service the pool until we fix 2 issues: a) we have black algae everywhere in spite of him dumping $10-$20 worth of chemicals weekly. Here is a link to an image of the pool with the algae: https://picasaweb.google.com/1034455269 ... 9322881810
b) the pool has a leak as we are loosing 2-3" of water weekly.
We have scheduled a leak detection to address the leak issue and hopefully it is not anything major.

As for the black algae, since the pool is 10 years old, he (pool guy) suggested re-plastering at ~$6500. This is too expensive for us and way sooner than we expected! He suggested that our short term alternative wld be acid & chlorine wash.
My pool guy has been shocking the pool and using chlorine and cleaning it every week but the black algae comes back within 2 days. He has not used any harsh chemicals such as algicides. We run the motor twice a day for 4 hrs.
I got in touch with the prior pool guy the prior owner of the house used. He (prior pool guy) did an acid wash 1.5 years ago but according to him the pool was not well maintained by the prior owner and cleaned it only on a monthly/bi-monthly basis.

So, my question is: shld we get over the sticker shock, bite the bullet and go for re-plastering? Or go for couple of other approaches before resorting to this last ditch attempt such as: 1) fix the leak, so chlorine level doesn't keep dropping and then shock, use algicide + daily brushing for a week to see if the black algae comes under control? 2) drain pool, go for acid & chlorine wash if 1) doesn't work?
We feel like our pool guy is only suggesting the expensive options and since there are so many other house related expenses, we need to know if we need the pool is going to be a high budget issue. Thanks in advance for all your help and suggestions.
 
Welcome to TFP.

Are you sure that's black algae, or are you just taking the pool guys word for it?

If you haven't determined it for yourself, scrape some of it off and rub it on a white paper. It will be green if it's algae.

What type of chlorine has he been using? liquid, powder, etc.

In order to give advice we need some test results and how you got them.

It's hard to tell from that picture but it doesn't look like the pool is in too bad a shape.

Your best course of action would be to read pool school, get a good test kit and take over your pool yourself.
 
A plaster pool that has not been well maintained will likely need replastering at 10 years old. I am in the same boat as you, as mine needs it too. The problem is any place where the plaster is rough or pitted, black algae can take hold. The only way to get rid of it is to use a wire brush to break it loose and open so the chlorine can get to the algae. I have to do this on my pool on a weekly basis to keep it at check. In fact I'll be in my pool tonight to take care of a spot that's popped up. And keep this in mind, my pool is properly maintained, but the BA still takes hold in those rough spots.

Now, you probably have a root cause of the issue beyond the rough plaster. I am betting all those years of "shock" and chemicals have raised your CYA so that you chlorine cannot do its job. The best way to determine this is to get a GOOD test kit and test on your own. We recommend the TF-100 at http://tftestkits.net. The second solution, with a "gotcha", is to take your water to a pool store. They will typically test for free. But, here's the gotcha - they typically do NOT test CYA properly. Also, don't let them sell you anything ... we can walk you through your pool without their expensive and sometimes WRONG chemicals.

Don't use an algaecide. BLEACH is the only algaecide you need. But, to get started on this, it is a must to know your pool's current balance, and that's why you need a GOOD test kit.

Regarding if that's black algae, it should not easily brush off or be sucked up by your cleaner. Black algae takes a wire brush and a lot of work to scrub off.

Acid washing is not necessary.

Read up on leak detection here:
pool-school/leak_detection

I'll also note that weekly chemical additions are not frequent enough. That's the #1 reason I don't have a pool service.
 
Thanks everyone for the prompt response. I checked the spots by scraping it and it is definitely green when I rub it on white paper. The pool guy used chlorine tablets in the pod and liquid chlorine.
I tried ordering TF-100 test from the website listed but it seems to be down. I will try ordering it on the website again later. To give you guys some numbers, I went to a local Leslie's to run the test. The tests came up as follows:
FAC: 5 ppm
CH: 250 ppm
CYA: 55 ppm
TA: 100
pH: 7.7
Copper: 0
Iron: 0
TDS: 1300
Pho: 100 ppb

Shld we consider chlorine wash then to get rid of the black algae for now? And then re-plaster later (maybe a year) when we save up for it? The plaster is definitely old as it comes out pretty easily when I scrape it in the steps. I will definitely run the TF-100 test once I receive it and post the results and update findings from leak detection.

Thanks.
 
If your CYA is 55, that is amazing. I was really expecting to see 100+.

You can't get rid of the black algae without scrubbing it. And I mean hard scrubbing with a wire brush. A wash will help, but I don't see the point in draining, acid washing, then refilling, when you need resurfacing.

I can knock plaster off my steps too. That's why in my other browser I'm looking at pool finishes.
 
You don't need to acid wash to get rid of the black algae. You need to scrub the spots with a wire brush and slam the pool (pool-school/shocking_your_pool).

To do this, you'll need one of the recommended test kits (pool-school/pool_test_kit_comparison). You'll need to be able to measure FC above 10, and to do that, you'll need the specific chlorine test type in these kits. Other test types won't accurately go beyond 5.
 
Thanks guys. I will follow your advice and scrub hard on a regular basis and shock the pool. And save up to do a re-surfacing soon. I have ordered the TF-100 test, will post results as soon as I get it and read up on pool school. Thanks again.
 

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Hello all,

So I did fixed the inlet and outlet leaks in my pump and got leak detection done as well. The good news is there was no leak in the pool, I think fixing the pump leak took care of the water loss. The leak detection company wanted us to replace the deck o seal for $700 as it is (according to him) currently cracked and allowing water to get between the pool structure and the pool deck. Here is my first question: Is it super critical to get this done? Or just another thing we can get to in a few years?

We brushed and scrubbed all the black algae heads with a wire brush and shocked the pool twice. I think we are free of black algae and we are keeping up the brushing each time we see any spot. I got the TF-100 test kit I ordered today and here are my results (ran the test 2 days after shocking):

pH = 7.8
FC= 9 ppm
CC= 0 ppm
TA= 160
CH= 480
CYA = 50

The results indicate that my pH is on the higher end which is also reflected by the alkalinity number I guess. I am a little thrown off by the out of range hardness number as well. So I guess second question is do I need to do anything about the higher TA (even though pH is acceptable) and hardness? Thanks in advance for all your help and suggestions.
 
To answer your questions: With TA and CH on the high side, it is important to lower your pH. You also need to lower your pH to slam that black algae or it will keep coming back (shocking twice is not slamming). Target 7.2 for your pH, and then start the slam.

Neither the TA nor the CH are in urgent need of adjustment; you can start the slam as soon as you get your pH down: pool-school/shocking_your_pool

Once the slam is well underway, test your fill water for TA and CH. What are they?
 
I got the pH down to 7.2 but the directions say the pool shld be free of debris. We have a bunch of trees above the pool and a lot of sand gets blown into the pool, I have cleaned up all the other stuff like leaves & insects. My automatic cleaner is having a tough time keeping up. What wld be the best & economical way to get rid of the sand? Also, do I need to wait to get rid of the sand before starting the slam process. James, I called the previous owner and found out that the pool was not painted, it was only acid washed in 2011.

Thx.
 
Go ahead and start the slam. The less debris, the less places available for the algae to hide. Organic debris like leaves consumes a bit of chlorine. But your pool doesn't have to be perfectly free of debris to slam it. Just keep it as free of debris as you can. Brushing will help keep the algae exposed to the chlorine.

I'm not sure of the best way to clear the sand out.
 
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