What is this discoloration?

[Bischinha]

We bought a home with a pool two years ago, and having no knowledge, have relied on the local pool store to test the water and recommend what chemicals to put in (we won’t be doing that anymore). We noticed this grey/blue staining in the Spring. It’s gotten worse over the Summer, despite the pool store saying our water was balanced. They are suggesting a drain and acid wash. So, a few questions:
1: What is causing the discoloration ?
2: How do we get rid of it? (Note the picture with the bright circle is where we let some acid sit inside a huge pvc pipe to see if it would affect the staining)
3. How do we keep it from coming back?

EDITED TO ADD:
~20k gal, approx 5 years old, spa with waterfall, pebble tec finish, cartridge filter, jandy pump, Dolphin nautilus cleaner

 

[ajw22]

Welcome to TFP.

Follow the stain identification process ...

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

What chemicals have you been using in the pool water?

 

[JamesW]

I think that it's copper. The only thing that might get it off without an acid wash is sulfamic acid. I would try that first.

If you can get it off, you would still have to drain and refill to get rid of the copper or it will just restain.

Draining the pool is risky because the pool can pop out of the ground if the ground water is high.

I would do the sulfamic acid (Jack's #2 copper and scale stuff) and then drain and acid wash any residual copper stains.

Acid washing is going to make the plaster very rough.

Don't drain the pool without knowing what to do to prevent the pool from floating out of the ground.

 

[Bischinha]

Welcome to TFP.

Follow the stain identification process ...

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

What chemicals have you been using in the pool water?

We *were* using chlorine pucks and muriatic acid (we are going to switch to what is recommended on TFP)

 

[Bischinha]

I think that it's copper. The only thing that might get it off without an acid wash is sulfamic acid. I would try that first.

If you can get it off, you would still have to drain and refill to get rid of the copper or it will just restain.

Draining the pool is risky because the pool can pop out of the ground if the ground water is high.

I would do the sulfamic acid (Jack's #2 copper and scale stuff) and then drain and acid wash any residual copper stains.

Acid washing is going to make the plaster very rough.

Don't drain the pool without knowing what to do to prevent the pool from floating out of the ground.

The pool could pop out of the ground?! Yikes! What is Jacks #2?

 

[JamesW]

STAIN SOLUTION #2 – The Copper & Scale Stuff | Jacks Magic

jacksmagic.com

Copper can come from algaecide, a heater or ionizer.

Do you have a picture of the equipment?

 

[ajw22]

The pool could pop out of the ground?! Yikes! What is Jacks #2?

Sulfamic Acid

Copper in Pool Water - Further Reading

www.troublefreepool.com

 

[ajw22]

We *were* using chlorine pucks and muriatic acid (we are going to switch to what is recommended on TFP)

What brand chlorine pucks ? Clorox Blue tablets?

 

[Bischinha]

STAIN SOLUTION #2 – The Copper & Scale Stuff | Jacks Magic

jacksmagic.com

Copper can come from algaecide, a heater or ionizer.

Do you have a picture of the equipment?

Twice in the last 12 months, we have used an algaecide for black algae (recommenced by the pool store) and we’ve used the heater maybe five times in the 2 years we’ve owned the pool.

Also, we have a salt cell, but after Hurricane Harvey, the water was so diluted, the pool store recommended switching to a straight chlorine pool (the salt cell was almost dead)—that was 2 years ago

 

[Bischinha]

What brand chlorine pucks ? Clorox Blue tablets?

We had a salt cell when we first bought the house—then it died, and Hurricane Harvey happened, so the pool store suggested switching to being a straight chlorine pool (since the rain had diluted the pool) since then, we have used pool life brand, Clorox blue, and since spring, in the swim brand tabs.

 

[JamesW]

What's the device on the wall to the left of the AquaLink RS?

I think that the stains are copper. Probably from algaecide, some from the heater, some from the Clorox blue tabs and maybe an ionizer depending on what the thing on the wall is.

How do you add the tabs?

What is the water chemistry history?

 

[Bischinha]

I haven’t any idea what that thing is—the previous owners left us no info. We usually put the pucks in a floater. For the most part (over the last two years) the water has been pretty balanced (I wish I kept the old print outs from the pool store) with the exception of adding the algaecide twice, we only usually need to add chlorine—occasionally muriatic acid, and we haven’t needed to shock the pool since April.

 

[JamesW]

It might be an ionizer or ozonator. Is there any information on it at all?

In any case, I think that the stains are copper.

It's only cosmetic, so you can ignore it if you want.

If you definitely want to get rid of the stains, I think that the solution is sulfamic acid treatment followed by a drain and acid wash.

Don't drain unless you're sure that you can do it safely.

Acid washing is very aggressive and will eat the plaster finish and make it very rough.

You can try ascorbic acid. Sometimes it works but sometimes it makes it worse. So, it's a risk.

Try crushing up some vitamin C and let the vitamin c sit on a spot for a while to see what happens.

 

[ajw22]

Clorox Blue tablets contain copper. Beware of any pool product that says “blue “. It is a code word for copper.

 

[JamesW]

Can you remove the cartridge so that we can see what it looks like?

Copper in the water will turn the cartridge a turquoise blue/green.

Sulfamic acid might not work. Once the stains get bad, they are not easy to remove.

Sulfamic acid should not go through the heater because it is aggressive to copper.

You might be able to do a no-drain acid wash where you lower the TA to zero and the pH to 4.5.

You would need to take the equipment offline and take other precautions. So, it's best done by a professional or under professional supervision.

 

[Neto]

I would ignore your pool store advice, of course they want you to not use a salt cell so you buy chlorine from them... A Jandy salt cell will run you about $600 and you will be back running as long as salinity stay within levels.