Metal Staining

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ejcom12

Member
May 7, 2022
10
San Antonio, Texas
Pool Size
40000
Surface
Plaster
Chlorine
Liquid Chlorine
First I want to say thanks to the great folks that contribute to this site! Taking ownership of my pool has been a great decision and I couldn't have done it without all of you!

I've had to do a couple of absorbic acid treatments in the last year due to metal staining showing up on the bottom of the pool. The stains look like discoloration on the surface of the floor. With the absorbic acid treatment the pool clears up almost immediately. I also noticed that my Polaris 280's white parts were starting to have an orange rust color to them and with the absorbic acid treatment it comes out looking brilliant white again, right away. This leads me to believe that the issue is iron, but I could be wrong.

I fill my pool with well water. This has not really been a problem for most of the 7 years I've lived here, but something must have shifted in the aquifer in the last year. So my question is, what's the most cost-effective way to prevent having to do the AA treatment over and over again? Here are my ideas, let me know which makes sense or if anyone has any other suggestions:

1. Continue to fill with "hard" water and use sequestrant periodically to bond to the iron.
2. Top off with "soft" water, which is filtered and softened by our whole home filter and softening system. My concern with this is that I've heard that it could cause degradation of the gunite surface.
3. Buy one of those filter attachments to stick on the end of the hose and help filter the hard water when I top off.
4. Do nothing to the water and live with AA treatments every once in a while.

Outside of these occasional stains, my water is crystal clear and my chemistry seems to be within suggested ranges by this site.

Thanks in advance for your thoughts.
 
ejcom12 said:
First I want to say thanks to the great folks that contribute to this site! Taking ownership of my pool has been a great decision and I couldn't have done it without all of you!

I've had to do a couple of absorbic acid treatments in the last year due to metal staining showing up on the bottom of the pool. The stains look like discoloration on the surface of the floor. With the absorbic acid treatment the pool clears up almost immediately. I also noticed that my Polaris 280's white parts were starting to have an orange rust color to them and with the absorbic acid treatment it comes out looking brilliant white again, right away. This leads me to believe that the issue is iron, but I could be wrong.

I fill my pool with well water. This has not really been a problem for most of the 7 years I've lived here, but something must have shifted in the aquifer in the last year. So my question is, what's the most cost-effective way to prevent having to do the AA treatment over and over again? Here are my ideas, let me know which makes sense or if anyone has any other suggestions:

1. Continue to fill with "hard" water and use sequestrant periodically to bond to the iron.
2. Top off with "soft" water, which is filtered and softened by our whole home filter and softening system. My concern with this is that I've heard that it could cause degradation of the gunite surface.
3. Buy one of those filter attachments to stick on the end of the hose and help filter the hard water when I top off.
4. Do nothing to the water and live with AA treatments every once in a while.

Outside of these occasional stains, my water is crystal clear and my chemistry seems to be within suggested ranges by this site.

Thanks in advance for your thoughts.
Click to expand...
Your #2 concern is unfounded. I suppose if you didn’t maintain the calcium high enough, that could cause degradation. But you can just added it if needed.

But you can also try filtering out iron with poly fill in the skimmers, do a search for some ideas on that.
 
PoolStored said:
A great read...just for you...

Ascorbic Acid Treatment - Further Reading

www.troublefreepool.com www.troublefreepool.com
Click to expand...
I appreciate your response. I did read that article, that's how I learned how to do the AA treatment, but the "how to keep stains from returning" fell a little short for me. Maybe I misunderstood, but it seemed like "replace with iron free water" is the only suggestion. I don't really have that option. It also mentioned CU-later, which I assumed only took care of Copper, but I will read up on it more.
 
Bperry said:
Your #2 concern is unfounded. I suppose if you didn’t maintain the calcium high enough, that could cause degradation. But you can just added it if needed.

But you can also try filtering out iron with poly fill in the skimmers, do a search for some ideas on that.
Click to expand...
Glad to hear that softened, filtered water may be a good option. I'll get to reading on poly fill. Thanks!
 
ejcom12 said:
I appreciate your response. I did read that article, that's how I learned how to do the AA treatment, but the "how to keep stains from returning" fell a little short for me. Maybe I misunderstood, but it seemed like "replace with iron free water" is the only suggestion. I don't really have that option. It also mentioned CU-later, which I assumed only took care of Copper, but I will read up on it more.
Click to expand...
You need to use sequestrant on an ongoing basis after AA, if you cannot replace the water.

From the article...

Ascorbic acid converts iron staining into dissolved iron in the water. Phosphonic acid (and other sequestrants) bind to the iron dissolved in the water and prevent it from redepositing as stains. However the phosphonic acid breaks down over time, so you need to keep adding more to keep the iron in the water. To some extent phosphonic acid can remove stains, but it isn't any where near as good at doing that as ascorbic acid is.

When there is iron in the water, low PH (say around 7.0 to 7.3) tends to prevent staining while high PH (say around 7.8 to 8.2) tends to cause staining. Phosphonic acid helps control this, so that high PH levels can occur without staining. High FC levels also tend to cause staining. As the PH goes up, and/or the FC level goes up, the chances of staining increase. Likewise, as the phosphonic acid level goes down, the chance of staining increases.

The top sequestrants are:
  • ProTeam's Metal Magic
  • Jack's Magic the Pink Stuff (regular)
  • the Blue Stuff (fresh plaster)
  • the Purple Stuff (SWG)
You can also find many other brands with similar products, some of which are noticeably less expensive. Sequestrants based on HEDP, phosphonic acid, or phosphonic acid derivatives are the most effective.[8]

A salt water pool is considered a high TDS water body.[9] The major component of that TDS are sodium ions (Na+). Because sequestering agents are anionic compounds (they have negative charges to them), you want to use a sequestering agent that’s formulated to work when there are higher concentrations of metallic species in the water. The Jacks Magic products formulated for salt water pools will give you the performance you are looking for.
 
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