New to TFP and need help with high cya and black algae

bunnybunbun

0
Bronze Supporter
Sep 15, 2014
19
Franklin Park, NJ
Hi everyone! This is a great site. I wish I'd found you years ago! I'm the original owner of a plaster pool and have always followed the advice of the local pool store that is affiliated with the company that built the pool.

For the first six or seven years, everything was fine with my pool. I treated the pool with 3" triclor tabs, weekly super chlorination with granular chlorine and bi weekly pro60 algaecide.

Then the problems with algae began. Although I had crystal clear water, I was getting green algae growing in the corners of the steps, around the pool light and in the skimmer intake. I would scrub it and it came off easily, but always came back. Chlorine demand was incredible. I would shock with huge amounts of the granulated chlorine and the next day it would be gone. This lasted a couple of years (I know, I should've acted sooner!) the pool store was useless in terms of advice. Finally, the pool company treated with copper algaecide and I thought all was ok.

In the meantime I switched to cal hypo shock because my CYA was very high. Of course, that in turn drove my CH up to 480. Then this summer, I inadvertently let the chlorine level drop. My chlorine dispenser stopped working and I started to notice black algae. Not much, but it was there. I scrubbed and scrubbed, used a silver algaecide and when the algae went away, I put a sequestering agent in for fear of staining. The black algae came back, still slight, but there.

After doing a lot of reading on this site, I decided that I needed to bring down the CYA and CH and drained 1/3 of the pool and refilled. Prior to doing that, CYA was well over 100, but this brought it down to 90 and CH to 360. Not low enough. Just this evening, I drained another 50% of the water and am in the process of refilling.

My last readings were
FC .5
TC .5
pH 7.2
TA 90
CH 360
CYA 90

My plan is to retest the water once the pool is refilled, SLAM with 12.5% liquid chlorine and brush it like mad (stainless steel brush). Thereafter to use the TFP method going forward.

My question to all of you is 'does this make sense'? I've been through so much with this pool the last few years and I want to get things under control once and for all. Is there anything else I need to consider ?

My pool company, who I am now furious with, came out to advise and told me I need new plaster, $7000 worth! The plaster still looks really good, to me. It is a little rough all over, like fine sandpaper, but I think this might be a bit of scale from the high CH. It is still white and looks thick. The pool company said I need new because when they brushed it, white dust came off in the water. Is that scale or I'd the plaster degrading? I want to ensure that I have exhausted all other options before re-plastering, so I'm spending the next few days on the above plan.

If you have any advice for me I'd be really grateful to hear it. Thanks so much! Sorry for the very long post!
 
Welcome to TFP!

Sounds like you are starting to open your eyes. :goodjob:

You certainly need to get the CYA down and then to follow the SLAM process to eradicate the algae.

If it is calcium scaling, you should be able to remove it by keeping the pH a little lower and lots of brushing, vCard alternatively, an acid wash will remove it, but also shorten the plaster life.
 
Thanks Jason! While waiting for the pool to finish filling, I took some snaps of the plaster. I must say, that I'm a bit worried about the grayish discoloration on the plaster. There has always been a bit of it, but seems to have gotten worse. Is this bad? Do I need new plaster after all? When there's water in it, it looks great.... image.jpgimage.jpgimage.jpgimage.jpgimage.jpg
 
So frustrating! I'm dying to get started with my SLAM only to find that Leslie's doesn't sell CYA reagent. It's like a conspiracy. My options at this point are to guess at the CYA, formerly 90 after 50% water replacement now 45? Or go all the way back to the store with a water sample. I guess I'm going to opt for the latter, but can I trust their read of the test? I really want this SLAM to work.
 
Leslie's is notoriously bad at CYA testing. Order some r-0013 reagent ASAP. A few days won't hurt to retest. Leslie's had 2 Oz bottles back when I first needed a refill, but it was about the same price there as it was to get a 16oz bottle from Taylor. You DO need to get some bleach in there Yesterday! !!
 
Thanks Timerguy.

I'm going to bring my test kit and sample to Leslie and run the test myself. I called and the guy and he said it was ok. Assuming my ph lands at about 7.2 again, do I need to bring it up before the SLAM? I recall reading somewhere that ph will go up during the process. Thanks!
 
Actually you want the pH down around 7.2 before you start the SLAM process.

Those grey areas do look like calcium scaling. A little hard to tell though. Certainly does not require new plaster.
 
Ok. Finally ready. I called around and was able to get some r-0013. I've balanced the water and here's my starting point:

FC 0
TC .5
pH 7.2
TA 100
CH 280
CYA 45

I'm going to shoot for maintaining FC of 18. Initial dose of 12.5%, 3.25 gals? Should I be going for 18 or more like 25 FC? Shock level or mustard algae level. There is no black algae visible, but I know it's there....waiting....
 

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Clearly there is something in the water consuming the chlorine. FC is only lost to the sun (you have a decent CYA level, so that loss should not be excessive) or organics in the water.
 
Certainly possible to have high CC especially with the FC dropping so fast. But, ignore the FAS-DPD turning back to pink, that does not count. Just do the FC and then CC tests fairly quickly and you are done.
 
Wonder if there is some ammonia in the water with the high FC loss and high CC's. You have CYA though. Prob not ammonia. Just thinking aloud.
Maybe take a FC test in 1/2 hour and see how much your FC drops. Try to get FC to 18.
When you test for CC make sure you go right to that test after the FC test. ?
 

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