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Jul 06, 2014
Pool water changed color after acid wash
by: Linda

About 4 weeks ago, our regular pool maintenance guy suggested an acid wash for our 8 year old salt system pool.

We trust him and agreed. The plaster is gray and white, which had previously given the water a medium blue color. The blue had lightened as the pool aged, and he (Dennis) said it would be somewhat darker after acid washing it. He drained the pool and did the acid wash.

However, when he refilled it, the water was VERY green in color. Looked horrible. There was a bit of an algae problem, which he quickly resolved, but the pool still looked green and cloudy. He then brushed the sides and vacuumed. Eventually, he was able to make the pool obviously clean. The water is clear, there are no algae, and chemicals are all within normal range.

Now, the pool looks green/blue, which is not a color I like. It is bluer than after it was first acid washed but still way too green. I miss the crisp clean blue color that it used to have. What would cause this color change? He doesn't really feel it's due to metals but is using a weekly metal removing product to be sure all metals, esp copper are not the issue.

The first dose went in yesterday, with the next due in a week. He also plans to power wash the pool and vacuum again. I do not see or feel plaster damage. I hope you can comment on what might cause such a drastic change in the water color, and what can be done about it. Thank you very much.

Linda P

Corpus Christi, TX

Thanks for the question Linda

Normally after an acid wash the plaster will become lighter instead of darker. I don't know why your pool guy would tell you otherwise, unless he did a test area and realized the plaster under the top layer of plaster was darker.

Most people do acid washes to brighten up their pools and make a lighter color.

It could be the plaster underneath was a lighter green/blue and that's what is coming through. I conferred with another well know pool guy and this was his response:

"My guess is the acid wash lightened up the grey plaster - not darkened it. Hence since it is lighter the Sun reflecting off of it will have a more greenish tint and less of a a dark blue. On cloudy days or early in the AM if the pool looks light grey then it is just the tint the Sun now produces."

I have never known the water to turn another color when an acid wash was done correctly. It may be as stated above, that the newly revealed plaster is causing the water to look a greenish/blueish.

If there are no metals in the water there's no need to use a metal sequestrant. It won't hurt to use it but is an unnecessary added expense.

If you'd like I can look at the chemical readings and see if there's something there. I need the actual number for that - Chlorine, CYA (cyanuric acid/stabilizer), pH, Alkalinity, Calcium Hardness, and Metals (iron and copper) and names of any algaecides you may have used along with clarifiers, phosphate removers, and/or flocs.

If they all check out the only other reason for the color change of the water would be the lighter color plaster.

If you feel your situation is more complex than this, I do phone consultations for a donation of your choice. It makes things go much faster and many people have found it extremely beneficial, saving them time and money in the long run. All your questions will be answered. I have nothing to sell you so you know I'm not bias.

Pool Consultation

Hope this helps and have a great Summer.


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