Caramel Colored Stains

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mmcwhorter

mmcwhorter

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Jul 13, 2015
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Huntingtown, MD
In the last 2 years only, when we opened the pool in April I saw caramel-colored stains at the shallow end steps and in the spa. They are a bit rough and do not think they are organic stains (as there were other darker stains at the opening that are gone by now, assume sunlight and CL2 got them)... I assume these that remain are calcium?

The top pic is the spa, the bottom pic is the shallow steps area. I am thinking I can easily drain the spa and use a one-gallon garden pump sprayer...perform a light acid wash. Should I use 50-50 water muriatic acid?

Another point, I usually dump salt onto the shallow steps as shown in the second pic (with the pump off for sure)...It may be my imagination, but I think the slowly dissolving salt might also be helping to eliminate the stains, as they seem to recede from the areas where the salt sits when dissolving. I don't mind draining the Spa and doing an acid wash to clean it up....but I hate to have to drain my pool to such an extent to remove the shallow end stains...I was thinking about a granular acid solution (risky I assume).

Another idea is to dump 40 pounds of salt into the bottom of the spa and see what happens?

The stains in person appear to be a little more light brown than the camera captured...caramel in nature.

Typically I keep the water well balanced, occasional pH bounces up to 8 but only for a few days until I beat it back down with 31.25 MA....Today I am at

FC=5
CC=0
pH = 7.5
TA=80
CAL= 325
CYA=70-80
SALT approx 3000

One other comment is I will admit that I have been keeping my FC rather high a my SWG is working better than expected...and sometimes it's been between 10-12 for many days on end.

Thenks to TFP SLAM process I employ each year at startup...The pool water always looks perfect, with the exception of these caramel-colored stains. And there are none in the deep end. If you can fix my problem with leaves......Otherwise, I really do have a trouble-free pool. :)

Ideas?

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If it is indeed iron, will a muriatic acid wash in the spa work to remove the staining? I assume if yes...the iron or course goes back into the water as a solution, and then I'd need a "Magic Jacks" type sequest agent to keep the cycle from recurring? Or perhaps I could drain and refill with a known "iron-free" source also. I sure hate to do that..... I wonder if the potential source of Iron might be from years of a tiny bit of overspray by the nearest sprinkler?
 
I put 5-6 1000 mg tablets each into two baby socks, added a pebble for weight, and tied the open end off with a rubber band. With pump off and out of six spots tested for no more than 1 minute each, three seemed to go whiter. The other three were not a noticeable change...maybe thicker concentration of staining material...assumed to be Iron? So, shall I buy a container of powdered AA? Also, I have several Chlorox 4-pound 92% sodium bisulfate bags (bought last year at season Walmart for $1 each :) And I have liquid 31.25 MA. I'll check threads here on the Blog on AA and Iron.
 
Put some of the dry acid in a sock and set on the stain. Only let it be for a minute or less. See if that changes the color.
That is the test for copper.
 
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MKnauss: Thanks and I have some 92% sodium bisulfate I can try. It appears the Vitamin C in a few places turned the "caramel staining" to white. Since the area more affected/stained is in the spa, is there any major downside to draining the spa into the pool and spraying with 50/50 water / MA? Other than 50/50? I assume quickly rinsing with a hose and refilling ASAP is the way to do it....and of course, keeping the highly acidic spa water out of the propane heater until it mixes back into the pool.
 
If you feel it is iron, then I would just add ascorbic acid to the spa, being sure the spa is isolated, mix that around for a few minutes, and then use a sump pump to drain the spa to waste. Again, be sure you have isolated the spa by adjusting your valves at the pad. DO NOT run the pool pump during this.

It does not take much ascorbic acid. After you get the FC to 0 (the initial AA add will do that) then it only takes about 1# per 10000 gallons to clear the stains.
 
I just tried 92% sodium bisulfate, 3-4 ounces in a man' crew sock.....with a pebble to weigh it down....about a minute on the stained area. Saw a milky cloud leaving the sock, when removed NO CHANGE to the stain...:confused:
 
Ahhh...now I understand.

I will follow your process for the spa...I think the spa is around 2000-2300 gallons, easily holds up to six people. In this case you are saying I need only 3-4 ounces...wow, that sounds amazing.... I will re-compute that spa water volume number to be sure. It's about 6-7 feet across, three feet deep in the middle, with a "bench seat" ringing the interior perimeter of course. I assume it's OK to mix the AA into a 5-gallon bucket and then pour it into the spa...sounds like it won't take long. Start the sump pump to drain one minute later. I'll use my winter pump that keeps the water below the tile line to drain the spa. I have a feeling that will take at least an hour. I'll advise the results.

Found 2 pounds for under 16 bucks here:


Looks like I can use the rest for "nutritional value" inside the house, who knew? :unsure:
 
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MKnauss: One more question: Will I need a sequest agent in the future to keep it from returning? Maybe I'll check my sprinkler water to see if it has Iron. There has been some overspray into the deep end over time. Or could it come from rebar when the pool was built? Thanks again.

BTW...I had copper staining in a different pool in FL...as I recall, it was almost black, charcoal. This staining is more caramel.
 
Iron likely comes from fill water. It builds up over time and plates out in areas of higher pH or FC. Spa is likely as it is sometimes heated. Not likely to be rebar, you would see distinct spots if that was the issue.

Copper is normally a greenish to bluish tinge. Purple if copper cyanurate. Black is typically silver. From metal ionizer devices.
 
After a bit more thinking (sorry), I wonder why treat the stains in the spa with AA and the Iron stains go away......instead of using a sump pump to waste for the spa water: why I would not be able to pull water from my pool (23,000 gallons) thru my skimmers and into the pump and circulate ONLY back into the spillover spa....Over time the spa and pool would reach equilibrium...I am thinking that perhaps 4-5 ounces of AA would not be much of a big deal in a 23,000 pool combined with a 2,300 gallon spa. The concentration of AA would be about 10% of what was used to eliminate the Iron stain in the spa. Would highly diluted AA be a future problem? Would the AA ultimately dissipate in the sunlight and CL?
 
You are adding the iron back into the water. When you release the iron from the surface, dump that water to remove the iron. Or it will stain again.
 
got that...and I really appreciate your support.

But my pool and "overflow" spa are interconnected. Use the same water. I was thinking of concentrating first on removing stains from the spa (it's more noticeable), then doing the AA treatment on the pool later using this process:

Ascorbic Acid Treatment - Further Reading

www.troublefreepool.com www.troublefreepool.com

My spa is overflow and in normal operation is intermingled with the pool water ....so I guess my only long-term treatment will be to follow the process above for pool and spa at the same time...and use a sequest agent...and out of curiosity, I will check my fill water for iron (the same source as my sprinklers, we are on a deep well here).

Also, my heater is not able to be isolated based on the way it was installed. I could "fix that"....but from what I can tell from the TFP process above, that is not a big deal to isolate it using AA for stain removal....as it is super gentle...and I keep an eye on my pH.

Some of the articles on Majic Jack's treatments for Iron say do not proceed if you cannot isolate the heater. I would think it's not using AA.

Thanks again.
 
I realize all that. But if the stains are prominent in the spa, by lifting them, and removing that iron concentrated in the spa water, you remove staining for quite some time. Lifting them in the pool can be a conventional AA treatment where you lift them and then manage the iron. But the spa is a small amount of water.

Up to you.
 
copy that, I see what you mean. I plan to start with the spa (drain it to waste as you say) and see what happens. I think I have been "over-chlorinating" using my pump too many hours and/or on too high an SWG % setting. I backed off both hours and setting recently. Also, my pool tends to have a pH bounce if I do not stay on top of it (could be aeration from the spa overflow???). Both of these attributes (high Cl and pH) I believe also add to my Iron Stain issues. But hey: the water is crystal clear!! LOL.
 
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I did an AA treatment of the overflow spa last year. Not sure where the iron came from, our fill water is pretty good. At least now. The stains were already there when we bought the house. The pool is about 40 years old, who knows what happened during that time.

My theory is that the staining in the spa was worse due to two effects:
1) Since it has a direct line from the SWG it will have higher FC and pH levels due to the freshly chlorinated water not getting as much diluted as in the main pool
2) The bubbler in the spa adds additional aeration and therefore faster pH-rise

I did what Marty recommended above: I isolated the spa, did the AA treatment in the spa only and dumped the water afterwards. The low level of staining in the main pool doesn't really bother me.

To speed up the process, I brought FC down to zero (again, only in the spa) with hydrogen peroxide. Like that I was sure that a small bag of AA would be enough. To calculate the right amount of peroxide, I used PoolMath: The amount of 3% peroxide needed to lower FC by X ppm is about the same as the amount of 6% bleach required to increase FC by X ppm.

The whole process was done in a couple of hours and I didn't have to worry about algae.

Even if you plan to eventually do an AA treatment of the whole pool, I would still start with the spa and dump the water. It's an easy and inexpensive way to get some iron out, rather than redistributing it in the main pool, where it would eventually have to get removed or sequestered. And for reasons above, there is likely a good proportion of iron contained in stains in the spa compared to the pool, making up for some of the differences in surface area.

Where are your returns? In the shallow end and the spa?
 
mgtfp said:
My theory is that the staining in the spa was worse due to two effects:
1) Since it has a direct line from the SWG it will have higher FC and pH levels due to the freshly chlorinated water not getting as much diluted as in the main pool
Click to expand...

Based on theory, we used to think that both pH and FC where higher in a SWG’s cell but in practice, due to the high flow through the cell, the pH is identical to the pool pH and the FC, at best, is 1-2ppm higher than the pool FC, which is nowhere near SLAM levels. I found this to be true by testing my SWG cell’s effluent. I would assume there still is a higher pH at the cell plate surface but I found no detectable change of pH in the return water.
 

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