Yellow (orange?) discoloration on horizontal and verticle surfaces

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T

tpribors

Active member
Aug 2, 2019
26
Las Vegas, NV
About 6-8 weeks ago I noticed some yellow or orange discoloration starting to appear. At that time it was mostly it was on the bottom surface and on the steps of the spa. At first it was some splotches in the deep. It’s not rebar rust – this is too wide spread and splotchy (and I've seen rebar rust and this ain't it :) ). I don’t know if the right term is “staining” but it’s become pretty wide spread now… At first it was on horizontal surfaces but in the past few weeks has appeared on vertical surfaces too.

I don’t believe it is organic. At first I thought the splotches were algae and I shocked the pool. It can’t be brushed away, and also resists scrubbing with the scrubbing pads, sandpaper and even scraping with a paint scraper. Sandpaper did get it off in a small test patch but it wasn’t easy and I could see plaster raising before the stain did. Also there is a spot on the seat in the spa so I drained the water down below the seat and tried acid and bleach on it, no effect.

stain 1.JPGstain 2.JPG
 
What would be an iron source that is this widespread? Our water (Vegas) is off the charts for calcium from the tap, but it doesn't have any iron hardness. The only source I can think of is the rebar, but I've seen rebar stains (a friend's pool) and they are much more localized and very dark and come from the "back". This appears to be a surface deposit.

I've thought about a dose of "Vitamin C" but what quantity would I use for a 21000 gallon pool, and is the proper bulk chemical ascorbic acid or acetic acid? Does it have any side effects, e.g., interaction with ph, chlorine, CYA etc? (Also, this is a salt water pool, so is it safe to leave the generator in place, and operational or disabled?)
 
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I just remembered I posted this. I tried many things. We had a drain and clean and they polished the surface of the plaster. It came back by fall. Everyone said yellow algae (I know, but I tried anyway, had nothing to lose for $20 of the yellow gone.)

Water test results never showed iron in the water. But then I saw something in the forum about some Clorox salt that had iron in it. Indeed we had drained and refilled the water about the time of the mention of this but didn't see it until recently as I was getting ready to drain and fill again this spring (due to high calcium from Las Vegas water - it starts off bad and gets worse, it's cheaper to drain/fill every year or two than use anti-calcium chemicals, plus I get to purge the dreaded don't-talk-about-it-here phosphates.) So anyway, I tried the Acetic Ascorbic acid (Vitamin C) treatment. 3 lbs from Amazon. Cleared the yellowing right up. It also seems to have reduced some splotching on the plaster which may be related, so I ordered some more and will see. Draining happens in Feb so hopefully all of the badness remains in suspension till then.

Edit: I used Ascorbic Acid not Acetic Acid. I had the Vitamin C note right just not the right name.
 
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@Donldson will correct me if I'm wrong, but I believe acetic acid is more inline with vinegar, while citric acid more with lemon. The reason I even mention this is that the type of acid directly impacts the type of stain (copper versus iron) and the anticipated results. Being a Vegas native myself, I joke about my innards being full of scale from all the garden hose drinking I did in the '70s as a child there, so exchanging the water every 1-2 years is understandable to control scale. But I would refrain from pool store potions at all costs and use the standard TFP-recommended products. If/when you see a stain, it's going to be two basic reasons - algae (organic) which will require liquid chlorine, or metals (iron/copper) while may require ascorbic/citric acid. Copper stains, are generally much more difficult to remove, typically come from pool store products unless you have a heater with an eroding copper core. Iron usually comes from a well, old plumbing, or perhaps high iron content city water.
 
PS. Your recollection of Vegas water is correct. The calcium content of tap water is nearly off the scale and it just gets worse. Between the calcium and phosphates (I truly have no idea where it comes from unless it is the pigeon s*** that blows off the roof into the pool) I'm on a regimen to change the water every two years. Lowering both makes the job of the salt chlorine generator much easier and subject to less swings. I know this place's position on phosphates but when it's low I have to run the chlorine generator at a combination of less time and less output. With new water I was getting by with running the pump for 4-6 hours a day (more as temp went up) at 40-50% output. Last fall I was up to 8+ at 60-70% (and in the last month, 80%) just to keep the chlorine at 4-5.

We're in the south part of the valley in Paradise which I understand has a higher native calcium level than other areas of Vegas, I suspect due to the age of our treatment plant.

Even with the water shortage the last fill added only about $100 to the water bill. This one might be a little more due to the rate restructuring around the Lake Mead situation but water here is still less than half the price of our water in Colorado front range (Lyons, which buys water from Longmont).
 
If you do elect to try and manage phosphates, be sure to grab something better than the products they sell at the local pool store. Look for a product online such as Orenda PR-10000 that is more concentrated. More info in the link below. Good luck!

Phosphate Removers - Further Reading

www.troublefreepool.com www.troublefreepool.com
 
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