Help! Is this calcium scale? Metal? Algae? I can’t identify!

[Timmy_C]

First thread here! See pics. I need help with my walls. I’m confused because the substance I’m trying to eliminate does sort of scrape off, but its extremely stubborn and there’s no way I can do it all by hand. It sort of seems to respond to Vitamin C but I’m not sure because it also seems to scrape off about the same with a pumice stone or a chlorine tablet. No method stands out as being more effective than another.

I purchased my home in February and this issue was present. There was a robot vacuum so the deep floor looks ok but staining appears on all walls and shallow floor. I had 1 ppm Iron and 3 ppm copper, and it sort of seemed like it would come off with citric acid in a sock, so I let my chlorine drop and attempted a citric acid treatment. For a few days it appeared the floors were better but I may have been imagining things. I used Metal Free in an attempt to remove the metals and I’ve reintroduced chlorine. The stains still look the same. I am unable to superchlorinate or SLAM effectively because my CYA is around 100 so I’m wondering if that’s part of my problem.

Since these “stains” sort of brush away, does that rule out metals? Do metals respond to brushing? My calcium hardness is also high at 800 ppm so I’m wondering if scaling is contributing to the problem.

I fully realize I should drain and fill since my water is less than ideal. But I can’t do this until fall or winter because I live in the oven of Phoenix. I’m leaning towards dumping 6 or 7 gallons of chlorine in there to see if it makes a difference. The most I ever did at once was 3 gallons and it seemed like it might have resulted in a small improvement but it’s hard to tell.

Thank you!
Tim
25,000 gallon plaster
36 sq ft DE filter, single-speed pump
FC 4.7 ppm
TC 5 ppm
pH 7.5
CYA 100
TA 98
CH 800
TDS 2000
Phosphates 0
Iron 0.1 ppm
Copper 0.3 ppm

 

[Wobblerlorri]

Can you brush it off? What does it do when you brush it? Does it come off in pieces or does it poof into the water?

I think you should do an Overnight Chlorine Loss Test to see if, in fact, you do have algae. Then we can see how to proceed from there.

Also, so a dilution test on your CYA to see just how bad it is. Dilute your pool water by half with tap water, shake, test that for CYA, and multiply the result by 2. If it's still 100, dilute it again and multiply by 4. And so on. At least you'll know how much you'll eventually have to drain and replace your pool when you can...

 

[Timmy_C]

Yes, it brushes off in most places I’ve attempted but it’s difficult. It neither comes off in pieces or poofs, it really doesn’t do anything when it is removed. In the pics you can sort off see scrape marks from my wire brush. But there’s no way I could scrape it like that with my fingernail. I’ll do the CYA test when I get a chance.

 

[Teald024]

Looks like calcium scaling to me. You definitely need to do a water exchange when the time is right.

How are you chlorinating the pool? I don't believe it is algae causing the staining, but your FC is low for the CYA level and you should add bleach to bring FC up per the FC/CYA Levels. Don't just dump bleach in the pool. If you decide you need to, then perform the SLAM Process. Dumping gallons at a time may turn your pool an emerald green color with all that copper in there.

You should invest in a good test kit from TFTestkits. I prefer the TF-100. This will allow you to test the water yourself and keep it balanced. With this, you can use the CSI to help remove the calcium buildup over time.

 

[Timmy_C]

I realize my FC is low for my CYA but it’s near impossible to keep as high it should be with the AZ sun. I am dumping bleach in the pool to chlorinate, dumping over the pump returns to circulate. How would you suggest I chlorinate?

I really appreciate the mention of calcium scaling. I thought this might be the case but couldn’t find any info about it on pool walls.

When you say “all that copper” you’re saying 0.3 ppm is a lot? So what is not a lot? 0.0 ppm? I guess 0.3 seemed low to me.

I also appreciate the mention of CSI, this is something I was not aware of. I’m at 0.86 which is obviously higher than it should be. Can’t wait to exchange this cruddy water. Just trying to get through the summer and also hoping to minimally improve my situation to make cleanup while empty a bit less work.

 

[Teald024]

Read through this article and this article about CSI and scaling. In your part of the country, monitoring CSI is useful to help prevent and possibly help remove scaling. A CSI of 0.86 is too high and you are seeing the effects. By adjusting pH, you can change the CSI and become more balanced

Have a read through Copper in Pool Water - Further Reading. While 0.3ppm isn't likely to cause staining yet, We have had folks dump lots of chlorine in the water and had it change to green water. Then realize copper was causing the problem and not an algae.

How much bleach are you using? Loosing 3ppm of FC a day can be common this time of year. So in your 25k gallon pool it is normal to go through 1.5 gallons of 6% bleach each day.
Once you get a good test kit, you can do a Overnight Chlorine Loss Test and see if you have an algae issue.

 

[JamesW]

Looks like scaling with iron and copper mixed in with the scale.

Lowering the CSI and vigorous brushing might eventually help reduce the problem.

Ascorbic acid might help reduce the brown some, but it might have a bad reaction with the copper.

Sulfamic acid might work, but it will lock up the chlorine for weeks.

Even if a metal treatment does work, the metal is still in the water and it will eventually stain again.

You can try to do a sulfamic acid treatment and then drain and refill if the drain won't cause the pool to pop out of the ground.

You can do an acid wash, but that really eats up the plaster.

Don't drain the pool without consulting with a local professional expert to make sure that draining and refilling won't damage the pool.

 

[Timmy_C]

I assumed it was typical to lose a fairly decent amount of FC per day during Phoenix summers... but I did not expect 3 ppm per day. That’s a lot of daily chlorination! I’ve been using 1 gallon of 10% chlorinating liquid every two days, administered after the sun goes down. By the end of day two, the chlorine is gone.

I had a feeling it might be calcium scaling but since I hadn’t read about it, so didn’t realize it was a thing. I guess at this point I’m trying to understand what sort of water treatments I should consider prior to draining and refilling, if any. I’ll read up on Sulfamic Acid. I posted a few more pics. I used a pumice stone on the floor yesterday to remove some spots of calcium buildup and the photos show the results. You can also see a path that the vacuum has left.

Thanks for all the input!
Tim

 

[JamesW]

Try running the pH at 7.2 for a few weeks and brush as much as possible.

Before draining, do a sulfamic acid treatment.

Don't drain without consulting a local professional expert to make sure that it's safe to drain and refill.

 

[Timmy_C]

I really appreciate all the input. I actually reduced pH to 7.2 last night because I recently learned that lower pH improves the effectiveness of chlorine. I’ll be diligent about keeping the pH low for the next couple of weeks and report back. As of today, things are the same. Water looks good with the exception of the scaling. I would assume any professional here in Phoenix is not going to be comfortable recommending or performing a drain and fill due to the risks associated with our sun and heat. I read a bit about sulfamic acid, results seem mixed. Hopefully I can achieve results via reduced pH without having to mess with sulfamic acid. We shall see!

If anyone has any other ideas of what I might try, please share. I’m open to experimenting. Thanks!

 

[ajw22]

I actually reduced pH to 7.2 last night because I recently learned that lower pH improves the effectiveness of chlorine.

Not if you have CYA in the water.

Does_Pool_pH_have_an_Effect_on_the_Chlorine.27s_Ability_to_Sanitize_Water?

In a pool with zero CYA, chlorine is more effective at lower pH, but this relationship is much less with CYA in the water to point of being irrelevant.

pH does affect the active chlorine (hypochlorous acid) level that is responsible for most of the disinfection of the water. However, when Cyanuric Acid (CYA) is in the water, it buffers this active chlorine so that pH has far less of an effect on it.

To be specific, with no CYA in the water, going from a pH of 7.5 to 8.0 has the active chlorine level drop by 50%. With CYA in the water, it drops by only 15%. Going the other direction, going from a pH of 7.5 to 7.0 the active chlorine level with no CYA increases by a little more than 50% but with CYA in the water it increases by 35%.

So we generally ignore the pH effect on chlorine except for a SLAM because the larger amounts of chlorine have the pH rise significantly so we recommend lowering the pH first before a SLAM, especially when it's a lot of FC due to high CYA levels.