Discoloration on wall

[danman]

Hello All,

I've attached some images, which were the best shots I could get of these black areas on my pool walls. I noticed this just last week, and I've been traveling a lot so it could have been there sooner. So Sunday, I tried the normal got my brush and quickly saw nothing was coming off. So I tried my wire brush(which I rarely ever use) and still nothing. I then read it could be black algae, so I started the shock process. I've had my pool running 24x7 since Sunday, and my chlorine level around 7-10 that whole time. Brushing it multiple times a day(morning and evening), but this morning I stopped the pump so I could get a good look at it and it's still the same. So.. could this still be black algae or is my pebble tech failing?

Pool was built in 2006

thanks for the help.

 

[Texas Splash]

Good morning. Could you provide a full set of water test results? That would be our first step. Water history may tell us if there are concerns for organic material, scale, etc.

Your signature shows a cell. Still using that? Any scale in the SWG cell? Have you added any other chemicals to the water other than muriatic acid or salt?

 

[JJ_Tex]

Have you added algaecide or anythying "blue" or with "minerals". If so it could be copper. I also put the pool school article on Black Algae, including how to scrape a bit off to see if it is truly black algae.

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.

www.troublefreepool.com

Stains in Your Pool

The stained pool is beyond embarrassing. Our in-depth Guide to remove stains in your pool will help you to remove the stains and prevent them in the future.

www.troublefreepool.com

 

[danman]

Good morning. Could you provide a full set of water test results? That would be our first step. Water history may tell us if there are concerns for organic material, scale, etc.

Your signature shows a cell. Still using that? Any scale in the SWG cell? Have you added any other chemicals to the water other than muriatic acid or salt?

I'm at work now, but I will post a results when I get home later this afternoon. So far, it's been pretty normal. FCL is about 3, pH(normal battle and try to keep it here) but around 7.4-7.6, CH is around 250, don't recall TA, but I don't think it was high. Anyhow I'll get you some numbers.

Still on the cell, and I only use Muratic Acid, and Salt. I will add liquid chlorine to help my cell out. It seems to really struggle during the summer even with my CYA at a normal level.

 

[danman]

Have you added algaecide or anythying "blue" or with "minerals". If so it could be copper. I also put the pool school article on Black Algae, including how to scrape a bit off to see if it is truly black algae.

Black Algae

This guide provides a step by step procedure for eliminating black algae in your concrete or gunite pool. Read full post here.

www.troublefreepool.com

Stains in Your Pool

The stained pool is beyond embarrassing. Our in-depth Guide to remove stains in your pool will help you to remove the stains and prevent them in the future.

www.troublefreepool.com

no algaecide or anything like that. Thanks for the articles, I'll read through them.

 

[kellyfair]

FC is low, even if you had no CYA at all. And of course CYA should be at least 60, if using SWCG. 70 is better. So with 70 CYA, you should dose up to target with LC, then run SWCG enough to replace what you use in a day.

In TX, I would aim for 11-12 as your target. With 70 as your CYA.

 

[danman]

sorry for the late reply, here's a test from just now.

FC = 7
CYA = 70
PH 7.4
TA = 120
CH = 250
Salt = 3100
Temp = 92

based on your chart Kellyfair I do need to raise my FC.

 

[Texas Splash]

Those are some very good numbers. If they are historically that way, I can't see why chemistry would be an issue. Still, if the color changes are fairly new, something is changing or reacting. To be sure it's not organic related, you might consider doing an Overnight Chlorine Loss Test. You may pass, but it's good to know for sure. Another easy test to perform as a formaility is to rub a stained area wiht a Vitamin C tablet to rule out iron. I'm not expecting any reaction, but it helps to rule out yet another issue.

Since the Pebble is going on 17 years, there may be an issue with its age, but we'll get some others involved in that discussions if needed.

 

[danman]

Those are some very good numbers. If they are historically that way, I can't see why chemistry would be an issue. Still, if the color changes are fairly new, something is changing or reacting. To be sure it's not organic related, you might consider doing an Overnight Chlorine Loss Test. You may pass, but it's good to know for sure. Another easy test to perform as a formaility is to rub a stained area wiht a Vitamin C tablet to rule out iron. I'm not expecting any reaction, but it helps to rule out yet another issue.

Since the Pebble is going on 17 years, there may be an issue with its age, but we'll get some others involved in that discussions if needed.

Thanks for the reply. I’m running the pump all night again and decided to raise my chlorine level based on that chart. I’ll test it again after 24 hours and see how things look and where my chemistry is.

 

[danman]

Hello all, here's an update. I've been baby sitting his thing since my last post on Friday. I've kept my Chlorine levels around 8-10, black spot's are slightly lighter but it could be in my head. I am losing about .5ppm of chlorine a day, not sure if that's still meaning I need to keep my level up or the sun that is cooking all of south east Texas is taking it. Anyhow, any thoughts? Also should my Calcium be higher?

reading from this morning at 7:30am
FC = 7.5
CYA = 70
PH 7.4-7.6
TA = 120
CH = 250
Salt = 3100
Temp = 90

 

[Texas Splash]

Your CH is on the low end, so no lower. If you don't add a little calcium, be sure to let the pH rise a little higher to compensate. A pH of 7.6-7.8 should be fine. Your FC seems steady which is good. If you decide to do an Overnight Chlorine Loss Test later, make sure to follow that page carefully and leave the SWG off. I would still try the Vitamin C test (iron) and perhaps try sprinkling a little cal-hypo granules on a stained area to see if they are organic.

 

[danman]

How would I perform these tests? Do I need to drain it to apply the Vitamin C, or just dive down and try to rub it on there? Or are you just recommending for the cal-hypo to just add it like a normal shock?

 

[Texas Splash]

Rub the Vitamin C tablet directly on the stain. Cal-hypo can be sprinkled on a floor stain or you can place some in a thin sock or nylon and rub it on a wall stain as well.

 

[danman]

ok cool, so you mean dive down and do these tests? for the Cal-hypo, I shouldn't just sprinkle it across the pool then. Just target that spot.

 

[Texas Splash]

Yes, dive down to wherever the stain is to get access to it. For the cal-hypo, sprinkle only on the stain to see if it's organic.

 

[danman]

Haven’t been able to do the vitamin test or cal-hypo yet, but I’ll try this weekend. Here’s some current pictures. I’m beginning to think it’s the pebble tech

 

[Texas Splash]

I’m beginning to think it’s the pebble tech

Does seem to have that look. Still, let us know how your testing goes this weekend just to be safe.

 

[danman]

I was able to dive down and take a look today, still working a lot. Anyhow, I don’t think it’s algae. Pretty sure my pebbletec is failing. Then googling I actually think I may have pebble sheen. But with that said, if it’s flaking and I can see small pits, anyone know an average cost to resurface nowadays? And how long can you let it go before fixing it?