Organic Staining

[nkk329951701]

I have this nasty stain at the bottom of my pool in several places, the pool company is trying to tell me it is black algae but from everything I have read black algae can not grow in above ground pool because it has nothing to root into. the water is clear. i have put a chlorine tablet and the stain lifts... these are my levels

tc 5
ph 7.4
ta 150
ch 250
cya 100

24 ft round 14,000 gallons, above ground

 

[frustratedpoolmom]

I had those exact stains. It's because your CYA is too high, and you don't have proper FC levels to keep the stains away. It's NOT black algae, the pool store told me the same thing. But 2 years of reading posts on this forum, I know it's not the dreaded Black Algae.

2 months after switching to BBB my stains completely disappeared and have not returned.

How did you get these test results?

You need to stop using stabilized chlorine sources like trichlor tablets and Dichlor shock. Stick with bleach/liquid chlorine. You need to drain at least half of your pool water to get your CYA in to range, if your CYA is accurate at 100. Since most tests only go up to 100, it could be higher. I would start with 1/3 of the water, at a time, refilling, recirculating, and retesting... then repeat a partial drain if necessary to get your CYA to at the very least 60.

My CYA was over 100, it took 3 partial drains to lower to 70, and then I left it there for the rest of that first summer. Then the following spring, I did another partial drain and got my CYA to 50.

Maintaining your FC levels according to the CYA chlorine chart will make them fade. But first you have to lower your CYA to a more manageable level.

Here's my stains, back in 2007, right after I found TFP and the source of my frustration:
http://www.troublefreepool.com/post5558.html#p5558

 

[nkk329951701]

the results came from the pinch a penny when I took them a sample, I retested it here my self today and I tested the cya to be about 80 and tc 4 and ph 7.6 and ta 150 the stains look like they are fading compared to last week. Does the cya need to be lowered.

 

[frustratedpoolmom]

Do you have a sand filter?

If yes, then you can decide to try to run with the higher CYA level, but you have to keep your FC up to the "Target" level at all times, and the stains should fade. If you look at the CYA Chart - you'll see your "min" and your "target" FC levels - based on your CYA. You want to dose each night 2-3 ppm higher than your Target...this elevated FC will make the stains fade. 4 is too low. Does your chlorine test higher than 5? Which kit do you have?

Do you know how to use the Pool Calculator?

If your FC isn't holding overnight, you should shock your pool, and that would be hard to do with CYA at 80.

With a sand filter, the CYA level slowly lowers overtime thru backwashing. So if you don't have a sand filter, I would go ahead and do a partial drain to get it down to 50.

Hope this makes sense. Sorry for all the questions.

 

[nkk329951701]

yes I have a sand filter.
The tc holds overnight and I added 2 jugs of it last night and you were right the stains seems to be fading..
Thanks so much for your help. When they are completely gone, I will update the pics..

 

[nkk329951701]

so I just went to the pool place and had my water tested. these are my levels according to them

tc 4.0
ph 8.0
ta 110
ch 300
cya 100

They told me to add alkalinity to raise it.. The only problem I have with that If I add baking soda, it is also going to raise my PH. Is the PH safe or do I need to add acid...

 

[nkk329951701]

I forgot to mention the stains are almost completely gone..

 

[reebok]

raise your alkalinity? why? if anything it could come lower if your ph is rising too fast for your liking.

 

[frustratedpoolmom]

You need your own reliable test kit. Don't listen to them. The PH is too high IF that's accurate, and the TA is fine.

If your FC is really 4 it's too low.

Maintain your FC according to the levels on the CYA chlorine chart...do not go below the min.

 

[ivyleager]

A CYA of 100 is livable. I've been there, done that. Levels go down thru backwashing and closing.

I will add that if when the cya is high and you need to run high CL levels, I found that I had to run my pump/filter 24/7 thru that summer. If I let the pump off overnight, I was battling algae even tho my CL levels were appropriate for the high cya.