stains in quartz pool

[myron]

Hello everybody,
I am a Mechanical Engineer from Greece and I have a problem which I wanted to share with you, hoping that you would be able to help me.
We constructed a new quartz aggregate swimming pool for a tennis club 5 months ago (25X10m and 1.5m of depth). The color of the quartz used was very similar to that of the sea sand so as to have a color of the water very similar to that of the sea. After 2-3 months of use the pool was in very bad shape. The pool couldn’t be cleaned and after meetings with the constructor of the pool and the constructor of applying the quartz we decided to empty the pool, to clean it with the use of a pressure washer and to apply sealers on top of the quartz surface in order to smoothen the surface and to avoid dirt and algae to remain between the quartz sand. I have uploaded some photos so you can understand how bad the pool had become. Before applying three layers of sealer we applied a layer of Algae stop liquid. I have to admit that the surface of quartz is not totally smooth but still has a rough surface.
After doing all that the pool was in perfect shape. The water was perfect and still is but one month after the filling of water, brown stains have covered the pool surfaced. The stains can be seen more clearly in a cloudy day. I have uploaded some photos and I hope they are clear enough. The water is being monitored all the time and right now it has the following chemical characteristics:
Chlorine: 0.82 mg/l
PH: 7.22
Reedox: 823 mV
Temperature: 25 C

The stains seem to have a slippery surface. The pool has being cleaned every day since the begging but that didn’t seem to help the problem.
I would be really glad if anyone could give me an advice about how to solve the problem.

Thank you for your time.

 

[linen]

Welcome to tfp, myron

I appears that no one has helped you yet...sorry about that

With that low of an FC level, it is likely the "slipperyness" is algae (unless you are saying that even dry they are slippery?). What is your cya level?

 

[myron]

Hello,
Sorry for my late reply but I was waiting for a chemical analysis of the water...

We don't use organic additives in our swimming pool.
Our water is pretty good as you can see from the chemical analysis.
The stains are slippery even when dry and I am afraid that is either a bad quality of quartz (with Fe inside) or not proper use of the finish resin.
Now I have cut a small piece of the quartz applied in the swimming pool and I am waiting for the chemical analysis....
I will let you know when I have more news.

Keep up the good work.

 

[duraleigh]

How do you chlorinate the pool?

 

[myron]

Hello Dave,
We use sulphuric acid (H2SO4) 20% in order to regulate the value of PH
Additionally we use salt (sodium chloride NaCl) and solution of sodium hypochlorite (NaClO) in order to regulate the FC level.

 

[duraleigh]

So, it sounds like you have a Salt Water Chlorine Generator and then supplement it with liquid chlorine, is that correct?

Do you add Cyanuric acid to your pool?

(I am going somewhere with this but want a better "picture" of your pool chemistry first)

 

[myron]

Yes exactly as you describe it.

We don't add Cyanuric acid or any other organic additives. I know it sounds strange to you but we have a different philosophy of the one that you are used to.

 

[duraleigh]

Well, I believe you have algae. The cure for that is to increase your FC level to about 8-10 ppm and hold it there until you eradicate the algae by brushing, filtering and keeping the chlorine up.

Your philosophy may not allow you to increase your chlorine to that level but it appears low chlorine has allowed algae to grow in your pool and increasing that chlorine is the only practical way to kill it.

Once the algae is gone, maintaining your chlorine around 3 ppm should prevent it's return.

 

[myron]

Dave I am not sure that this is the problem. Before filling with water the swimming pool, we applied a solution of an anti-algae all over the surfaces.
When the swimming pool was full of water we shoked the water with increased levels of FC and let it stay in that state for 24 hours to avoid algae.
The strange thing is that the stains are only on the bottom of the swimming pool!! The walls are perfectly clean.

Our next step will be chemical examination of the stains and of the quartz applied and I will inform you about the resurts as soon as I have them.


PS: I have upload 2 new pics to see how it looks now

 

[duraleigh]

The new pics do not look like algae to me, either. Rather a mineral deposit.

Here, an easy way for us to tell is to crush some vitamin C tablets and place them directly onto the stains (inside an old sock) for 2-3 minutes. If the stain is lightened, it is a metal stain.


Conversely, you can place a tri-chlor tab (or any solid source of chlorine on the stain for about a minute and if the stain is organic, it will be lightened.

 

[myron]

I have tried the vitamin C test but without any success....

I am afraid that there is a strange chemical reaction between the resin film and the quartz layer... that's why I am having a chemical test of the stain.

 

[duraleigh]

Best of luck. I am out of ideas.

 

[JamesW]

After 2-3 months of use the pool was in very bad shape.

What exactly do you mean by "very bad shape"?

Before applying three layers of sealer we applied a layer of Algae stop liquid.

What specific product did you use as the layer of algae stop?

What specific product did you use for the layers of sealer?

Can you post all of your pool and fill water chemistry including pH, TA, Calcium Hardness and iron levels?

Can you post all chemicals you have added since filling?

 

[myron]

ITEM UNITS RESULTS LIMIT
p.?. ( 25 ?C ) p.H. units 7,2 6,5-9,5
Conductivity ( 25 ?C) ?s/cm 2040 2500**
Total Hardness mg CaCO3/l 273 ---
Carbonate Hardness (temporary) mg CaCO3/l 14,0 --
Hardness non Carbonate (permanent) mg CaCO3/l 259 ---
Total Alkalinity mg CaCO3/l 14,0 ---
Alkalinity CO3 mg CaCO3/l 0 ---
Alkalinity ?CO3 mg CaCO3/l 14,0 ---
Alkalinity ?? mg CaCO3/l 0 ---
Chlorine mg Cl/l 466 250
Nitric mg NO3/l 17 50
Nitrite mg NO2/l <0,01 0,50
Ammonia (NH4) mg NH4/l <0,02 0,50
Calcium (Ca) mg Ca/l 85 ---
Magnesium (Mg) mg Mg/l 14,5 ---
Sodium (Na) mg ??/l 296 200
Potassium (K) mg ?/l 5,2 12
Manganese (Mn) ?g Mn/l <1 50
Nickel (Ni) ?g Ni/l <1 20
Copper (Cu) ?g Cu/l 22 2000
Iron (Fe) ?g Fe/l 5 250
Chromium (Cr) ?g Cr/l <1 50


ITEM UNITS RESULTS
Colony number in 22 ?C c.f.u./ ml 0
Colony number in 37 ?C c.f.u./ ml 0
Total coli forms c.f.u./100 ml 0
E. coli c.f.u./100 ml 0


I can only send you the photos of the products that we used for algae and for the sealer.

We only use anorganic products for the swimming pool as: sulphuric acid (H2SO4) 20%, salt (sodium chloride NaCl) and solution of sodium hypochlorite (NaClO)

 

[Patrick_B]

That is a pretty sophisticated set of test results, so I am naturally curious how you obtained them. Nothing wrong with them, just wondering. I am wondering however if the one you list as Chlorine isn't Chloride...? Interesting too that they give you bacteria colony counts.

I'm more curious why you are using Sulfuric acid instead of HCL. Is it not available in Greece? If you can get it, I would suggest using it instead to avoid adding Sulfates to your pool. I can't weigh in on the coatings, but I am very curious to learn more about them.

 

[myron]

We gave a sample of the our pool water to a chemistry lab. We can not have all those tests indoors.

We do have HCL but the pool constructor prefers sulfuric acid, I will ask more about it and get back to you.

 

[Patrick_B]

I'm sorry, I don't understand what you mean about not being able to have the tests indoors.

 

[myron]

sorry for the missaderstanding. I mean that I can't have all those tests without giving a sample to a chemistry lab.
We have a monitor where one can see at any time only the values of PH, chlorine, reedox and temperature of the water in the swimming pool.

 

[Patrick_B]

Ahh I see. Well, that is quite the battery of tests they provide.

 

[JamesW]

After 2-3 months of use the pool was in very bad shape.

For the pool to be in very bad shape after only 3 months, the quartz/cement product, installation or chemistry must have been very bad. If it was the product or installation, then it should be under warranty. What do the product manufacturer and installer have to say?

Was the pool stained, scaled, etched or something else?

Before applying three layers of sealer we applied a layer of Algae stop liquid.

Proper water chemistry will prevent algae. There should not be any need for algaecide. In any case, the algaecide that you used is not made to be applied as a pool coating. It is designed to be added to the pool water. It will cause multiple problems with the sealer. Also, how can the algaecide prevent algae if it is under sealer?

As far as I can tell, the sealer that you used was not intended to be used under water in a swimming pool. Do you have any reference that specifies that the sealer was suitable to be used as a swimming pool coating?

Here is the only product that I can find of theirs that is made for pool usee.
http://www.marispolymers.com/product_ca ... l-coating/