Help - Unknown Stain taking over Pool - Cannot Be Removed

dpatou23

Member
Aug 5, 2020
8
Greece
Hello,

My first post here and a new pool owner so bear with me for any negligence!
I have recently installed a white fiberglass pool for my hotel business and for the past month or so I have witnessed a light brown stain/film (please review pics) developing randomly on the walls and the floor of my pool. As time passes it's slowly taking over the pool and I have yet to find a solution. Touching it barehanded, it does not feel any different from the gel coat.

FYI, I have tried scrubbing by hand and with a nylon brush, scrubbing with Vitamin C tablets, scrubbing with chlorine tablets and scrubbing with a sock, a pole and muriatic acid (PH-). None of these methods seem to work.

I check chemicals daily and my readings always fall in between these ranges:

PH 7.2-7.5
FCL 1-3
TA 50-100
CYA 50-100

My pool installer insists that I lower the PH to 6.8-7.0 and the stain will slowly dissolve as she believes it is metal/iron deposits from the refill water I use (local municipality).
I am not certain I should do this as I have customers who will be using the pool until the end of September! If I lower the PH, I'm afraid I may cause a health issue to a customer but on the other hand, if I don't do anything I'm afraid this stain will only get worse!

Finally, and just to add some more suspense, I am in Greece! Which means I do not have access to stain ID test kits as I cannot find vendors sending these kits here! And if they do send, it ends up double the price and at least a month delivery. As an example, to buy a proper water testing kit (Taylor 2006C) I have to pay 100 dollars extra just for delivery! (I know, I have to and I will buy it eventually)

Any ideas or any assistance will be highly appreciated.

P.S. I have recently purchased the Lo-Chlor Multi Stain Removal and No More Metal products. I intend on using these in October when I close off the pool.
 

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Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Hello and welcome to TFP! :wave: For your first post, you did a superb job illustrating your issues. :goodjob: Maybe it's just me, but I'm having a hard time seeing the stains in the pics. :crazy: You've exhausted the top-3 test options we would advise you (i.e. Vitamin-C, dry acid, chlorine tablet). I would be curious to know how the products you recently ordered work. I agree though that lowering the pH much more probably won't help much. I don't see any benefit to lowering the pH any more than 7.2. Due to the limited test supplies in your area, some processes will be challenging, but based on what you have available, we hope we can help provide you with some guidance.
 

dpatou23

Member
Aug 5, 2020
8
Greece
Curious about one thing though ... how do you chlorinate the water? Liquid chlorine or something else? Your FC is a bit low for this forum based on our FC/CYA Chart.
Hello and thank you for your quick response.

In these pics the stains do look more subtle than real life. The best representation of real life conditions is on the outline of the bench where you can see a deeper contrast in colors. The proper pool color is the white outline.

I chlorinate the water with multi action tablets recommended by my pool installer. To be honest I was kind of suspicious of these as they are supposed to be a "Chlorinator-Floculant-Algaecide and PH Stabiliser-All-In-One!".

The main ingredients of these 200 gram tablets are:

Trichloroisocyanuric acid

Aluminum Sulphate (Floc)

Copper Sulphate (Algaecide)

I read up on these and they seemed to be pretty legit and commonly used ingredients for swimming pools. Although there is no indication of % concentration of each chemical in each tablet.

After reviewing your Chlorine/CYA chart & video I intend on following it to see how the pool works. However, isn't a high ppm of chlorine a possible hazard for guests? Shouldn't I be better off trying to lower CYA by draining the pool partially?

As for my initial post, do you have any more recommendations? Or should I just wait it out till October and see what the Lo-Chlor products can do?

Thank you again for your time.
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I think one of your problems could be related to those tablets. The aluminum and copper are bad for the water. In time, those levels grow and cause staining. Copper is especially bad, and the only way to remove metals from water is to do a water exchange. if not at all at once (often dangerous for the pool itself), then in stages so that over time the metal concentration drops very low. Metals become aggravated when the FC and/or pH get elevated. Tablets also tend to drive the pH and TA down because they are acidic, while increasing CYA because they also contain stabilizer. Generally we do not recommend using tablets on a long-term basis.

In the meantime, I would find a source to buy liquid chlorine or regular bleach. Same thing just different strengths. The main ingredient is sodium hypochlorite and it exactly what you want to give the pool each day to maintain the proper FC level.
 

dpatou23

Member
Aug 5, 2020
8
Greece
I think one of your problems could be related to those tablets. The aluminum and copper are bad for the water. In time, those levels grow and cause staining. Copper is especially bad, and the only way to remove metals from water is to do a water exchange. if not at all at once (often dangerous for the pool itself), then in stages so that over time the metal concentration drops very low. Metals become aggravated when the FC and/or pH get elevated. Tablets also tend to drive the pH and TA down because they are acidic, while increasing CYA because they also contain stabilizer. Generally we do not recommend using tablets on a long-term basis.

In the meantime, I would find a source to buy liquid chlorine or regular bleach. Same thing just different strengths. The main ingredient is sodium hypochlorite and it exactly what you want to give the pool each day to maintain the proper FC level.
Actually the water is somewhat new as I finished construction works around mid-May this year and completely cleaned and gradually replaced about 70% of the water by the end of May. If the problem is the tablets then I'm really surprised -and disappointed- that this can happen so soon and so easily!

I'll try replacing these tablets to see what happens. I'll have a look around the forum for dosages and frequency of liquid chlorine. I'd be much obliged if you can point me in the right direction. Cheers
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
I'll have a look around the forum for dosages and frequency of liquid chlorine.
You can use our PoolMath APP or the older PoolMath webpage. Both of those have features to show you how to determine how much of any product is required to go from a current amount to a future goal or target. If the APP, look for the menu "Effects of adding chemicals", and on the webpage you use to two vertical columns (Now & Target). If you have any questions with either product, let us know.
 

dpatou23

Member
Aug 5, 2020
8
Greece
You can use our PoolMath APP or the older PoolMath webpage. Both of those have features to show you how to determine how much of any product is required to go from a current amount to a future goal or target. If the APP, look for the menu "Effects of adding chemicals", and on the webpage you use to two vertical columns (Now & Target). If you have any questions with either product, let us know.
I'll let you know of the outcome, thank you for your assistance
 

dpatou23

Member
Aug 5, 2020
8
Greece
I think one of your problems could be related to those tablets. The aluminum and copper are bad for the water. In time, those levels grow and cause staining. Copper is especially bad, and the only way to remove metals from water is to do a water exchange. if not at all at once (often dangerous for the pool itself), then in stages so that over time the metal concentration drops very low. Metals become aggravated when the FC and/or pH get elevated. Tablets also tend to drive the pH and TA down because they are acidic, while increasing CYA because they also contain stabilizer. Generally we do not recommend using tablets on a long-term basis.

In the meantime, I would find a source to buy liquid chlorine or regular bleach. Same thing just different strengths. The main ingredient is sodium hypochlorite and it exactly what you want to give the pool each day to maintain the proper FC level.
Hello again,

I'm expecting to receive Sodium Hypochlorite (13%) in the next couple of days and I need to ask you another question if you don't mind.
I could only find 33kg plastic jugs of this sanitizer and I'm concerned of it's shelf life. I've read around that it will only last 2-3 weeks. From your experience is this true? What happens if the vendor has it lying around for a year or so?

If however this is not true, could I order this sanitizer in bulk and keep it for next year also? FYI, I intend on storing it indoors in a cool and dry storage area.

Again, thank you in advance for your help.
 

cowboycasey

Gold Supporter
LifeTime Supporter
TFP Guide
Jul 3, 2013
4,425
Fletcher, OK
Hello again,

I'm expecting to receive Sodium Hypochlorite (13%) in the next couple of days and I need to ask you another question if you don't mind.
I could only find 33kg plastic jugs of this sanitizer and I'm concerned of it's shelf life. I've read around that it will only last 2-3 weeks. From your experience is this true? What happens if the vendor has it lying around for a year or so?

If however this is not true, could I order this sanitizer in bulk and keep it for next year also? FYI, I intend on storing it indoors in a cool and dry storage area.

Again, thank you in advance for your help.
Wow, I had to get the google on this one :)

33kg = 73 pounds
73 / 8 pounds per gallon = 9 gallons

You will be fine, you should be able to use 9 gallons within 2 to 3 weeks... The strength does go down over time, how much I am not sure.. In a year you will not have 13%, it will probably be down to 4% or so but that is a guess.. there are people here that know how to get the amount it will fall to...

The vendor probably fills it from a container that was probably 15% when it got delivered and it sounds like they are commercial so they probably go though it very fast... :)