Light Brown/tan Spots/streaks

[cardopa1]

I have been having this problem the past couple of years. I get large brown patches and streaks throughout the bottom of my pool. It must be algae because if I super shock with 4 gal of liquid chlorine it disappears. As soon as the chlorine level comes down a little to maybe 10 it re-appears. It doesn't scrub off. It seems/looks like a stain but it can't be because heavy chlorine does the trick. Keeping the pool heavily chlorinated knocks off my ph. What is it ? How can I get rid of it permanently ?
My ph is 7, cya 80.

 

[RobbieH]

Since it's easy, and Zea just posted this on another thread, I'm just going to post his comment.

Hi, welcome to TFP! Shock is a process and not a one-time application of product despite what the bags of shock say. You will need to raise your pool to shock level and keep it there as much as possible until you pass the 3 criteria for completing the shock process. Read shocking your pool and defeating algae for more information on the shock process.

Any possibility you could have metals in the pool? Well water, pool store products (list what you've used), etc.

 

[PSW]

Do you have a SWCG? If not, CYA of 80 is high. Not enough FC is the cause for the stain re-appearing (assuming it IS organic).

 

[cardopa1]

I have been using test strips and can't get accurate reading when the free chlorine is high after I shock the pool. I know from here that when super shocking I need FC levels related to my CA which can be FC of 20 - 30. I went to Leslies to buy a test kit as suggested here but looking at it and talking to the person, it doesn't look like I can determine FC readings over 5 with the kit. I know that's wrong from this site but how do I get readings over 5 from these kits ? They all have the glass that goes up to 5. Better yet, the guy at the store says I never should have readings of fc over 5 but instead in the 3 to 5 level. Please help - I'm confused.

 

[Bama Rambler]

The problem is that they don't sell the correct kit. What they sell is the equivalent of the k-2005. Be sure to get the one with the FAS-DPD test. Not just the DPD test.

 

[cardopa1]

Hi,

I bought a TF100 test kit and tested water for the first time:

- the chlorine instead of yellow was orange/red color
- PH 6.8
- FC 100
- CC 0
- TA 90
- CYA 35

Help !

 

[Vette]

The chlorine from the OTO only goes up to 5. The OTO test is the one in the Taylor Basic kit in the blue box. That's usually only used by those of us here to check to make sure we have chlorine. (if there's no chlorine, it will be clear)

FC 100 isn't right. Did you multiply by 5 instead of .5? On the tests it says multiply by .5, think of it as dividing by 2. If you used 20 drops, your FC is 10.

 

[cardopa1]

Sorry - I was wrong the FC is 50 (not 100). I added 100 drops until it turned clear.

So the readings were:

- PH 6.8
- FC 50
- CC 0
- TA 90
- CYA 35

I didn't get a chlorine reading from the basic kit because instead of turning a yellow color it was orange/red !

 

[Vette]

I didn't get a chlorine reading from the basic kit because instead of turning a yellow color it was orange/red !

That's what its supposed to do. The basic OTO test can only read up to 5. If you really have FC of 50, it will be orange. That test it only useful for telling if you have chlorine. If there wasn't chlorine, it wouldn't turn a color when you put the 5 drops of reagent in.

The PH test also isn't as accurate when FC is above 10.

 

[cardopa1]

I assume I leave eveything alone since the FC is 50 ? My CYA of 35 indicates I should have a shock FC of 14 (mine is 50!)

 

[Vette]

Hopefully you don't bleach out your liner. I would certainly let it fall to 14 before re-dosing (if it needs it)

 

[Swampwoman]

Can you post a picture of the stain, or take one next time it appears?

 

[cardopa1]

I will get pictures and post. Even with a FC of 50 I still had some real light spots.
Readings for today:

FC 27
CC .5
TA 70
CYA 50

My FC went down from 50 to 27 and all the large patches and streaks are back.

 

[Swampwoman]

Hi there. At the beginning of this thread you reported cya of 80...then cya of 35. Are you confident it's 35, and that the 80 was a misread? Just checking, because cya is neither created nor destroyed...except by addition or splash out!

So, if you have some vitamin c in the house, can you mush some up in a sock and hold it against the stain and tell us what happens?

Chem geek might be the guy to know, but I am wondering if when you supershock to four times your shock value, you aren't just kind of oxidizing the stain (if for example it actually was iron, let's say) into a particulate state than then resettled. Don't know if this is chemically conceivable, but something fishy is going on with this stain by the sounds of it.

What level do you normally keep chlorine at? Do you ever let it fall? How often do you have to lower your ph? What is your water source? How old is your vinyl? You're in ground, right? Have you always used bleach, or previously pucks? Are there any signs of corrosion around your light,
steps, etc.?
My only concern is that if it's metal, you might be exacerbating the situation with such high
shocking. I am personally working on my own layman's theory about these things as I get
confirmed iron streaks and spots too.

Which reminds me, do you fully dose with sequestrate and then sustain dosage weekly? Hopefully
we can help you figure this out
Cheers!

 

[onBalance]

It is possible that the soil/dirt underneath your vinyl liner has micro-organisms growing, such as mold, mildew, algae, bacteria, etc. Those micro-organisms can actually grow through the liner and create a "stain like" looking problem, which doesn't scrub away. A high dose of bleach will temporarily kill it (or bleach the color away). But yes, it will return as the chlorine level drops. Unfortunately, probably the best remedy is to remove liner and sterilize the soil. But sometimes a treatment with iron sulfate around the perimeter of the pool and soaking it in may solve the problem. I hope this isn't what is causing your "staining."

 

[cardopa1]

Hi All,
Readings today:
PH 7.0
FC 21
CC 1
TA 70
CYA 50
CH 220

So my FC has come down from 50 to 27 to 21 (which for my CYA is about shock level) but I have my tan patches.
The CYA of 80 the other day was a mistake.
I tried the sock of vitamin C and it didn't work.
I have an inground. Vinyl liner is about 7 years old. I always keep my chlorine high and as a result my PH is low.
I have always used the 3" inch tabs but switched to bleach 2 - 3 weeks ago.

I hope its not from under the liner as onBalance says - how can I determine that ?
I tried to attach picture but it was too big in size

 

[Swampwoman]

Well, a CC of 1 usually means indeed you are fighting something organic, and that you need to maintain that shock until it clears (less than 1 ppm chlorine loss overnight, plus less than .5 cc, plus clear water.)

Re Vitamin C, by "didn't work" you mean you held it to one spot for a few minutes and there was no color change? That would normally suggest that it's not metal staining, and as the cc suggests, is in fact organic.
-- Also, did you add more CYA to get to 50 from 35? Or are you still tweaking/practicing reading the CYA? It's important to get that number nailed so that your shock level corresponds. You might try using the "mustard algae" shock levels.

I would be interested in hearing from OnBalance how to tell if it's a "behind-the-vinyl" scenario as well

 

[JasonLion]

You need to get your PH in range. To do so, you need to let the FC level come down to around 10 so the PH test will work. High FC levels tend to make the PH test read higher than actual. Since your reading is low, the actual level could be lower still, which could be part of the problem.

Can you post a picture of the stains?

 

[onBalance]

I have owned a large pool service company for 35 years. Only once, about 15 years ago, a vinyl liner pool developed a dark stain on the bottom bowl. I tried MA and dry acid on it. I tried chelating agents, alum, and other chemicals. Nothing removed the stain. I swam down to the stain and tried scrubing it. Nope, didn't work. Then I tried liquid bleach and cal hypo directly on top of it. Both removed the stain immediately. But within a few days, the stain return, and if I remember correctly, in the same location. I called a vinyl company and asked about this situation. They confirmed that micro-organisms can pass through vinyl and made some suggestions to remedy. So I hired a vinyl liner company to come out and replace the liner and sterilize the soil beneath the pool with concentrated chlorine bleach. That worked. It is my understanding now that vinyl companies add a fungicide/biocide type chemical during the manufacturing process to inhibit such situations.

Cardopa1 has used liquid chlorine bleach and it has removed the stain temporarily. The pH should not be low since bleach raises the pH. It is probably a testing issue. The vitamin C didn't work, and I don't think MA will work either. Perhaps it should be tried. But I think that Cardopa1 has the same problem I encounter once before.

 

[Swampwoman]

On balance, that's very interesting, because there is a slight possibility that one of my longer, faint stains is actually something like that, despite the fact I do indeed have an iron issue as well. So thank you for the information -- our liner is 12 years old so there will likely come a time soon whereby we will want to replace/re-sterilize the soil. I was wondering though, about treating with iron sulfate...wouldn't that be introducing iron runoff? And further, could iron-laden water used on a nearby terrace possible gather in a sump located BENEATH the pool and percolate through to reach other side of vinyl? Just curious...I have a sump under the pool designed to offset a terrace, hill and river...talk about interesting site management

Okay, so just a thought for the OP...borates are fungicidal...I wonder if treating to 50 ppm might help if this were the case and if the poster did not want to be on the hook for a new liner? Or if at such a low concentration same would be effective. Might be an interesting experiment -- and cheaper than a new liner. But that said, you wouldn't want to fool around with borates until you have your PH sorted out, per Jaon's comment.