Acid Wash for Stains? How Best to Proceed?

[JSpool3]

"Last summer", while I was on vacation it seemed the Pop-Ups stopped working, and or the skimmer got clogged. I ended with some lines of stains going out radially from the Pop-Ups. I cannot brush them out. I have a 20 yr Pebble-Tec pool, 10K gallons, Salt Water, and I use a Pentair Chlorine Generator and a Pentair Auto Acid Dispenser. I am planning to empty the water due to water hardness in the next few weeks. Since I am emptying the pool, should I go ahead and acid wash? I have never acid washed before, but a pool company has. I am a bit hesitant on an acid wash, as the Pebble Tec is rough in a few places (and I have never done an acid wash). Suggestions please on how to best to proceed?

Attached a picture showing the stains. Also follwing is the chemical measurements from the pool store. But admittedly since it is winter here is Arizona, I have let the Chorine get really low.

Date​

Overall Score​

View PDF​

Free Chlorine​

Total Chlorine​

pH​

Alkalinity​

Calcium​

Cyanuric Acid​

Iron​

Copper​

Phosphates​

Salt​

Issues Reported​

Instore Test​

02/15/2023​

50​

View PDF​

0.18​

0.18​

7.7​

83.0​

528​

32.0​

0.1​

0.3​

107​

3348​

None​

 

[reggiehammond]

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You could very well have algae and metal stains - a bad combination. Pool store testing is notoriously inaccurate - please review pool basics and consider buying a trust worthy test kit. The best pool is the pool you care for...

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[ajw22]

Let's have @Dirk repeat his story of how an acid wash destroyed his pebble pool.

The stains are cosmetic. I would not risk a 20 year old pebble pool finish to remove cosmetic issues.

You don't know how much palster is remaining holding your pebbles together. An acid wash will remove plaster that anchors the pebbles. If the acid removes too much plaster you can have much of your pebble finish come loose.

Have you tried stain chemical treatments to identify the type of stains?

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

Stain ID Kit | Jacks Magic

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[Dirk]

I wouldn't acid wash a brand new finish, let alone an old one. Acid washing does not magically attack stains without touching anything else. The acid eats away a layer of plaster, which takes the stains with it. How much plaster is up to the skill of the person performing the wash. How much stains depends on how much plaster is removed and how deep the stains are.

In my case, not only did they not get much more than 50% of the stains, they took off way too much plaster and it left the finish rough and pocked. A few days later coin sized bubbles formed in the plaster which then peeled off. The acid wash destroyed the finish, which was less than four years old at the time.

There's a very long thread around here somewhere in which I describe what happened and how I got the contractor to replace my entire finish. Suffice to say, you would not likely win such a case because of the age of your finish.

More to the point: (1) don't acid wash your pool, save the money for the replacement someday (soon, it sounds like), and (2) if you regularly employ a person or pool maintenance company that has suggested an acid wash on a 20-year-old pool finish, you should fire him.

 

[Dirk]

Oh, one more thing. My pool was emptied to perform the wash, then refilled. That's when I noticed the pock marks and roughness. It was then emptied again, because the contractor wanted to try and sand out the imperfections (which didn't work), then refilled a second time. It was after that fill that the bubbles formed.

In the course of the litigation, I had a plaster expert analyze the damage. His theory on the bubbles was the acid wash weakened the plaster, and then by removing the water the second time, which removed the pressure the water was applying to the weakened plaster, the bubbles formed.

And I believe that problem is not a one-off, but rather a known issue of old plaster. Removing all the water from an old finish can result in weakened plaster popping off. Think twice about emptying your pool. You can exchange water to adjust the chemical balance without removing water. It's called a "no drain exchange."

This page, about halfway down:

Draining - Further Reading

www.troublefreepool.com

 

[JamesW]

Do you have a heater?

If you're going to drain and refill anyway, I would try a sulfamic acid treatment.

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

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