Whole Pool Stain, Rough Plaster at Season Open

[squirrel49]

Hi,

I opened our pool a few weeks ago. It was a fairly easy open and the water was sparkling clear within a day or two (and still is). However I noticed that after vacumming and running the dolphin multiple times most of the pool surface still had a light tan/brownish stain. The pool was stain-free when I had closed it last fall.

I have tried multiple tests to determine the next course of action, but am unsure of what to do next. Here is what I have done so far:

1. Added 1/2 Gallon followed by another 1/2 Gallon of a sequestering agent (GLB Sequasol) -- No Change.
2. Brushed, brushed, brushed.... -- No Change.
3. Placed granular clorine in a sock and put underwater on a stained area for 30 minutes -- No Change.
4. Placed PH Down (Sodium Bisulfate) in a sock and and put underwater on a stained area for 30-minutes -- No Change.
5. Tried the ProTeam Metal Magic Test (Sponge soaked in Metal Magic on stained area for 5min, 15min, 30min) -- very very slight change in stain after 30 min.

Other info:

1. I usually top off water throughout the year with well water.
2. My daughers say the pool surface is extremly rough. It has always been very smooth (we brushed endlessy after marcite when we built two years ago).
3. The Pool is a 28,000 gallon gunite with a standard white marcite finish. The spillover spa is a diamondbrite finish. The spa had a similar tan/brown stain on it when opened, but I drained and scrubbed with a mild muratic acid solution (1 part acid, 4 parts water) which seemed to do the trick.

My current numbers:
FC: 1 (was higher earlier, still adjusting the SWG)
CC: 0
TC: 1
Ph: 7.4 (was over 8.0 when I opened)
Alk: 100
Cal: 220
Cya: Unmeasured

I am unsure what to next. It appears that whatever metals were suspended in the water last year precipitated out over the winter. Any help anyone could offer would be greatly appreciated.

Pat.

[mbar]

It would be good to get a cya measurement. I am wondering why you would have gotten stain with a low chlorine level - did you shock when you opened the pool? Or maybe they happened when you closed with high chlorine. High chlorine along with high ph will let the metals precipitate out of the water and stain the surface of the pool. Since you have already tried just the sequestering agent and did not seen a lightening of the stain, you may have to use the regular stain treatement with ascorbic acid - usually if the stain is old it is more stubborn and needs the ascorbic acid. Here are some links you can use to buy it:
http://www.chemistrystore.com/Ascorbic_Acid.htm
or

http://www.msm-msm.com/store/agora.cgi?cart_id=%%cart_id%%&product=Vitamins&user4=Ascorbic%20Acid

Here are the directions:
Take your chlorine down to 0, if there is chlorine in the water it won't hurt, it will just eat up the ascorbic acid, so you will need more to get rid of the stains.
You will need about a half to one pound of ascorbic acid per 10,000 gal. I like to go lighter on it and see if all the

Put the filter on circulate.
Use a cup and go around the perimeter of the pool and drop it down the sides as you go.
Let the ascorbic acid circulate for 1/2 hour. You will be amazed how the stain just disappears before your eyes.

If the stain is not all gone, leave the filter in circulate and add more ascorbic acid close to where you still see stain. Leave it in circulate until all of the stain is gone. (add more ascorbic acid if it circulates for 1/2 hour and there is still stain)

When the stain is gone, add enough sequestering agent for the volume of your pool - more is better than not enough.

Put the filter back on filter and leave it on 24/7.

The ascorbic acid will bring your ph down, after 24 hours you can start to bring up your ph and alkalinity - use baking soda first, it will raise both ph and alk. Make sure you test in between, because you don't wantyour ph to go any higher than 7.2. If your alkalinity is in range, and you still need to raise your ph, use Borax to take it up to no higher than 7.2. After 48 hours you can start to bring up your chlorine. You want to do this slowly. It will take a lot of chlorine - I prefer to use bleach only at this time, and try to take it up to your minimum chlorine for your cya according to the "best guess chart" Do not shock! Do not shock for at least 2 weeks! Make sure you keep your ph low for (7.2) for a week or two - it won't be hard because the ascorbic acid will help it stay low. Once your chlorine starts to hold, it means that you have used up the ascorbic acid in the water and it will be easy to rebalance the pool back to your regular parameters. You may want to use a polyquat algacide as a deterrant to getting algae while your chlorine is low.
Let me know if you have any questions.

[waterbear]

I am curious what your calcium was when you closed the pool. It almost sounds like scale deposits to me.
Edit: we tend to forget that calcium is also a metal.

[squirrel49]

Thanks for the replies so far.

A little more info.

1. I didn't measure CYA because I was out of the regents I need. I'll try to get a measurement tonight.
2. I don't remember if I closed with a high chlorine level. I did use chlorine-free shock when I closed.
3. I shocked with chlorine (bleach) when I opened.
4. I also tried crushed up vitamin C in a sock-- didn't seem to make a difference.
5. Checked my log... Calcium was at 350 when I closed.

Pat.

[mbar]

The reason I asked about the cya, is that mine usually is gone when I open my pool in the spring. If the cya is low, then the chlorine is much more potent. Your calcium last year was fine. :)One of the reasons I suggested the ascorbic acid treatment is that you said you used a solution of muriatic acid on your spa to get rid of the stains. I think the ascorbic acid would work. I know that on my fiberglass pool some of the stains felt rough to the touch, I don't know if it is a little scaling with the stains, but the ascorbic acid removed it. I have also used a light sandpaper to remove some stains that were very localized. You may be able to use a pumice stone. It is worth a try if the stains aren't too large. Just rub gently, because you don't want to take much of the surface off - just the stains. Hope thsese ideas work. Let us know how you do.

[waterbear]

Thanks for the replies so far.

A little more info.


5. Checked my log... Calcium was at 350 when I closed.

Pat.

Your calcium dropped 130 ppm while the pool was closed. I suspect it has deposited as scale, which is often seen as a rough white or tan deposit! Acid and/or abrasive scrubbing will remove it. You said your pH was over 8.0 when you opened. High pH is one of the factors that will cause scaling. You might try dropping your pH to 7.0 for a while to see if it helps redissolve any of it but the only solution might be an acid wash if it is really bad. Anyone else have any ideas on this?

[mbar]

I read somewhere that the scale that is brown is scale that formed over some dirt. This may have happened over the winter since there was such a calcium drop with high ph. I would do as Waterbear suggested. Take the ph down to 6.8 to 7.0, then brush the surface of the stain - even using a pumice stone. If the area of the stain isn't too big, this should do it, otherwise you will probably have to have the pool acid washed. Let us know how you do:)

[squirrel49]

Thanks for the replies.

I'm pretty sure you're all right on the mark. I think it is calcium scale. I went swimming tonight with a snorkel mask and inspected most of the pool. The surface is extremely rough (feels crystaline). It covers the entire pool, other than the foot or so that was not under water over the winter (that part is smooth). On the bottom, and all steps, it is tan, and on the walls and vertical surfaces it is white or colorless. I have a Merlin mesh safety cover that lets in fine silt over the winter so I think what I have been calling stain is actually dirt-covered calcium scale. This did not happen in prior years, but I don't remember opening at such a high ph level before.

I am willing to do whatever it takes to get rid of it. I would like to try every alternative other than draining the pool. The pool is appox 28K gallons and costs ~ $900 in fill water to fill it. I'm sick to my stomach because our pool plaster has always been baby smooth and now it feels like volcanic lava.

I will first try dropping the PH to ~ 7.0 and do a lot of brushing. So far brushing doesn't seem to do too much. I only have a nylon brush, should I buy an aluminum one? Is there anything else I should be doing? I don't know that a pumice stone is an option. The scale seems to be on every square inch of the pool.

Btw, my cya level is ~50.

Thanks,

Pat.

[Lenny]

Have you had any luck, Pat? I have the same problem, although maybe not as bad as you. Tan stains and roughness. I have a mesh cover too.

This is my second opening. The first closing was right after completion of the build, so I think my plaster has still been curing and causing my PH to get high very fast after closing. Both years my PH was sky high upon opening and my hardness and alk were both low.

Tomorrow I'll try dropping the PH and giving it a good brushing.

[squirrel49]

No luck yet. Consensus seems to be that I will have to drain and light acid wash or sand/buff to remove the roughness. I am trying anything I can to avoid that. The pool is relatively new (2 1/2 years).

We have dropped the PH and we brush twice a day now and my wife optimistically thinks is is getting slightly better --- I don't really see any difference yet.

This is my second opening as well, both with a mesh cover. One difference is that the first year I had not yet started the salt system on my pool, so it was closed and opened as a fresh water pool. Opened fine, plaster as smooth as ever. I brought the Salt system on-line last year, so this was the first year it was closed/opened with salt water. Could this be a contributor? Are you running a SWG?

[Lenny]

I am running a SWG and installed it last year.

But there are so many people around here who've been using these. I've gotta think the word would be out if that was really a contributor.

[Lenny]

Actually, I wonder whether the mesh cover has more to do with it. I pumped my water down a good 16 inches at closing and it filled up pretty quickly this year. I even pumped a bit out at one point. And then if was full to the top again by the time I opened.

By the time I open my hardness and alk are very low. I'm thinking I'd have been better off with a solid cover that keeps the rain water from diluting the pool water. Not sure what the alk and hardness of rain water are, but I'm thinking it's not optimal ;)

[squirrel49]

Lenny,

I've had the mesh cover since I built the pool.

1st year, no SWG running, drained 18" water and closed pool. Over the winter, water level rose, I drained again at one point in the spring, prior to open. Opened to clear water, silt, worms etc on bottom. Vacuumed, shocked, balanced water, everything was great, plaster was clean and smooth.

2nd year, SWG operational, drained 18" water and closed pool. Over the winter water level rose, I drained again at one point in the spring, prior to open. Opened to clear water, silt, worms etc on bottom. Vacuumed, shocked, balanced water, but this time everything was not so great. Extremely rough pool walls and bottom with the horizontal surfaces tan/stained in color. To date, nothing has been successful in removing.

My in season water balancing, closing, and opening procedures did not change at all. I am not convinved that the SWG and saltwater pool had anything to do with my problem, but it is the only change I am aware of, so it at least makes me curious.

Pat.

[waterbear]

The difference might be that you did not keep close watch on your pH once you installed the SWG. They have a tendency to cause pH to rise and if you let that happen you could create scaling conditons.

[squirrel49]

During the season I keep a very close watch on my Ph (test daily using Ben's kit) and usually end up adding muratic acid weekly to keep within range.

Ph was 7.4 when I closed last fall. When opened this spring, PH was extremely high (>8.5). I'm not sure what happened over the winter or if Ph rise during the non-operational Winter period is normal or not.

[Lenny]

Same with me. I was all over the PH during the season but it was sky high both times I've opened so far. And Hardness and Alk very low.

I'm still hoping my problem is scaling. But I'm worried that the water pulled calcium from the plaster.

[thomas_CT]

squirrel49. have you heard of a product called hydroquest 100? I read about it but haven't tried it, maybe someone that has can chime in. It's certainly a better alternative than acid wash, imho. And if this application doesn't help your stain problem maybe Ascorbic Acid Powder can. "jus my .02 cents."

[Lenny]

Well, I took a closer look at my steps today. I tried some crushed vitamin C to see what that did to the stains. Not much. But now I believe I have it figured out.

I can see that it's a rough surface on top of the plaster rather than the plaster being pitted. I believe the stains are just scale encapsulated dirt. Does that make sense?

I used a pumice stone and it does work but it's slow and I'd go through an enormous amount of pumice. I'm going to try wet sand paper and see how that goes. Does anyone have recommendations on what would work best for this?

I'm still not sure why this happened and why it's so extensive. It's mostly on the horizontal surfaces. I know that the hardness was low when I opened. Before I closed, the hardness was low and I added a reasonable amount of powder to get the hardness within range. I may have added some after the pump was off and circulated the water with a sump pump and long hose. Is it possible that the calcium not being circulated enough could have caused a problem?

Does anyone know anything about this hydroquest 100? I love to find something that would help reduce the manual work I have ahead of my trying to sand this stuff down.

Thanks,
Lenny

[squirrel49]

Lenny,

I too believe that the condition I have is scale encapsulated dirt. I have tried the pumice stone with just about no luck (a whole stone for very little if any impact).

I am looking at purchasing an air powered underwater orbital sander and diamond pads in an attempt to sand the plaster underwater. I do not want to have to drain and refill this year.

Pat

[ezpool]

Any luck with this? I've been following this thread closely since I'm in the same boat. I closed a perfectly clean pool last winter and opened to a green, algae-filled mess. After cleaning everything up and getting my numbers in line, the water is clear but I've got tan stains throughout the pool. I've super-chlorinated for an extended time and also tried a sequestering agent after 4 lb of ascorbic acid. The stains remain. I've been brushing almost daily with a metal brush but haven't seen a change. I've had some luck with a "Stain Eraser" but that's not an option given the amount of staining. I was wondering if a pressure-washer would help? Anyone tried using a pressure-washer underwater? Will it even work?

[Lenny]

I got in the pool for the first time yesterday and was very relieved. For whatever reason, my steps were by far the worst. They had the scale build up and encapsulated dirt (although they are slowly getting better). There are stains around the pool floor (shaped sort of like thin leaves) but the floor and pool walls, overall, are pretty smooth. Not as smooth as last year, but not nearly as rough as I feared. One I take care of the stains things will be fine.

I think I'm going to get a rougher brush and keep working on the steps. I think they will eventually be OK as well.

I still don't know exactly what happened here. I'm going to try some asorbic acid on the floor stains to see what happens. I did add a metal sequestering agent a few weeks ago but that didn't do much.

ezpool, I don't know about the power washer. Maybe you could try it with extreme caution but I'd be worried about pitting the plaster and making things worse.

Lenny

[Lenny]

Well, I have tried crushed asorbic acid tablets on a few stains and it hasn't done much of anything. I basically have 3 types of things going on:

1. The rough areas, mostly on the stairs, which seem almost like sand is encapsulated in scale.
2. Many brown stains around pool. They are shaped like a thin leaf or sliver mostly. They look like metal stains. I put metal free in a couple of weeks ago and it didn't do much if anything.
3. Generally lack-luster plaster. The plaster looks dirty in general. It just isn't the off white color it's supposed to be.

Any ideas on how I should attack this? I inspected a lot of the pool yesterday with goggles. There are a lot of areas, like in the stair corners for example, where it looks like etching (or pitting) took place over the winter but most of the plaster doesn't approach the roughness of the stairs. I'm just not sure what to do about these stains. I'm thinking about treating with asorbic acid just to see what happens.

Any suggestions?

Thanks.

[squirrel49]

Well, I've decided to drain, acid wash, and sand the pool. The rough, slightly stained plaster is driving me nuts, especially since the plaster used to be so smooth. We have quite a few neighborhood kids that use the pool and they now have to wear socks or water shoes to keep from tearing up their feet.

I plan on doing it his weekend. I'm all set on the acid washing part. Is there any advice on the plaster sanding (diamond pad?, wet/dry sandpaper?, grit?, sanding tools, etc).

Thanks,

Pat.

[MaryS]

Pat,

I opened my 2 year old 18,000 gallon gray plaster pool this year and found the same problem that you have - very rough surface. I have always been meticulous about my pool plaster. When I closed it, the water was in balance and the plaster baby bottom smooth. Now it is a disgrace. I have been running it acidic for the past 2 weeks and brushing and sanding. The steps are a bit better, our swimsuits are finally safe. The sides are still very rough. The appearance of the plaster is just not what it used to be, not to mention the feel of it. The service company who closed the pool said the PH must have gone up too high over the winter, causing scale.

I am curious... are you going to acid wash and sand the pool yourself? Is this a difficult process? Let me know how you make out. I am trying to decide what to do.

Thanks
Mary

[mbar]

You know I have never heard of so many people having this problem. Just something that is very curious - I usually open my pool to very low ph. This year my ph was above 8 - I wonder what went on this winter? I live in northeast pa, where are you all from? It just has me a bit puzzled as to why so many have posted about scale on their plaster pools.:(

[MaryS]

I am located in Southeastern PA, a western suburb of Philadelphia

[Lenny]

Mary, I'm in Wilmington, DE.

That's the thing that bugs me about this. We don't know how it happened and we have no idea how to prevent it. When I closed my pool for the first time in 2005 my plaster hadn't cured yet (pool was built late in the season) so I wasn't surprised my PH was high at the start of my first full season. The plaster was pretty smooth at that time though. I would have expected my PH to have been somewhat better when I took off the cover this year but it was sky high.

What king of cover do you guys have? I have a mesh cover and I'm still wondering whether that can be a negative because it's exposed to the elements. My hardness was very low as well. I had to pump a lot of water out this year due to winter rain, so the the mesh cover caused the water to get quite diluted.

[mbar]

I have a mesh cover as well. There was so much rain this year - I'm sure I had almost all new water:eek: It just shocked me that my ph was high this year, when it usually is so low when I open.

[squirrel49]

Marie: I live in Southeast Michigan.

Mary: Yes I am acid washing and sanding myself. Shouldn't be too bad. Looks like I'm postponing another week. The water haulers are backed up at least a week and I want to re-fill as soon as I'm finished (don't want to leave the pool empty for a week).

Lenny: I have very similar situation to you. I completed building my pool late summer 2005 and opened on Labor day weekend. I closed that fall and had no issues on the subsequent open. I have a Merlin mesh cover.

Picture of clean plaster prior to the problems:
http://i19.photobucket.com/albums/b178/squirrel49/IMG_0988.jpg

[mbar]

What a beautiful pool! Hope all goes well:) Let us know how it turns out.

[Lenny]

Great looking pool, Pat.

After you do this, please let us know some details when you have a chance. I'm wondering about the materials and procedure in case I have to do it next year.

It really concerns me that we took the time to close like we're supposed to and still had problems.

Thanks.

[MaryS]

Lenny,

My pool was completed Memorial Day weekend, 2005. The pool company had me keep it open until November so that the plaster could cure. When the pool was opened in April 2006, the opening PH was 8.4, but no problems with the plaster - very nice and smooth. I maintained the water chemistry over the summer last year. The PH keep drifting up, but I expected that with the Salt Water Chlorinator. I just added acid every week to keep it within the range. Pool was closed Oct 2006 and reopened early April this year. Opening PH was 8.2 this year with loads of scale. We do not have a mesh cover. The cover is solid. Still not sure what caused the problem and what I should do.

Pat,
What a beautiful pool you have! Tell me, what is the procedure for acid washing? How hard is it to do?

Mary

[MaryS]

Pat,
Now that I have looked more carefully at your photo, I think we used the same pool tile. Great taste! ;-)

Again, good luck and keep us posted!

Mary

[PoolNewbie2006]

I have the same problem here in SoCal where the water is very hard in my area. I went into the water for the first time and was disappointed with the amount of roughness on the horizontal surfaces. I used my fingernail to scrape off a few of the rough spots and it was a combination of white and sandy (dirt covered scale) deposits. I had feared the worst because my SWG cell was heavily covered in white scale and not producing chlorine.

Anyhow, I want to try the method Waterbear has suggested in lowering the pH down to around 7.0 and brushing but have a few questions. No matter how much muriatic acid I add, it always seems to run high, ~7.8. That being said, I've been told not too add more than about 1/3 of a gallon of acid per day. At that rate, it will take forever to lower the pH. So...:

1) Is it safe to add more than 1/3 gallon at a time?
2) How long is it safe to keep the pH at that acidity level?
3) Are metal brushes generally safe on plaster?

Thanks in advance.

[Lenny]

Hey PoolNewbie2006,

Wow. I can't imagine why you need so much acid. How big is your pool? You might have a problem with your test method. I'd look for verification of that. Make sure your acid is a good strength as well. Yours might be 14% or even less. I'll bet one of these things is your problem.

I would add more than 1/3 gallon if I had to. Just do it slowly in front of the return. It's getting diluted quickly.

I've been using a metal brush. It honestly hasn't done much more than the nylon one so far. It certainly can't hurt.

[waterbear]

If your plaster is fully cured a metal brush will not hurt it. In fact, on fully cured plaster a combo brush of stainles steel and plastic bristles is what you should be using for normal brushing.
As far as adding acid. I would add it a pint at a time for each 10000 gallons, wait about 30 minutes with the pump running, test your pH, and repeat until your pH is where you want it.

[PoolNewbie2006]

Thanks guys. My pool is not large, 14,000 gallons. I think the reason my pool requires so much acid is a combination of the water in my area having a high pH level and aeration due to the spill from the spa into the pool. It is set to return part of the water into the spa when the pump is running during the day.

As for my test kit, it's shameful but I am still using the basic test kit provided by my builder. I've been planning to order the Taylor K-2006 kit online since none of my local pool supply stores carry a FAS-DPD kit but just haven't gotten around to it.

Off to the pool store I go to pick up my combo brush. Wish me luck and thanks again!

[thomas_CT]

THIS wORKS !!! and i swear i'm not affiliated with the Company!
I had the same problem as squirrel49. Rough plaster, Calcium buildup with dirt encased and i also have a salt/generator. At first i didn't try much just super shocking without success. Well i followed this thread in hopes of finding a solution. After squirrel49 stated he was going to buy a sander i began looking into alternatives. i came up with H100 acid, but i didn't have success rate to back it up. Then i Came across a Chemical plant in PA that stocked a solution designed to remove scales and minerals from tanks and pipes. After talking to the Chemist he suggested i stick with a pool product and suggested i take a look at a company in FL that makes a great product for removing scales. i visited their website and their it was:"(STAIN SOLUTION #2) is designed to safely and effectively remove copper stains and scale from all types of pool surfaces without draining the pool. In most cases, The Copper & Scale Stuff is more effective than acid washing the pool, and will save both time and money. Please Note: must bypass heater when using this product." i contacted the company and went through an intensive phone list trying to find the product in my area without success. On the second phone call, i requested contacts for the neighboring states. Finally i found a distributor in Boston who gave me a contact in My State (Connecticut) i took the 1hour drive and purchased the recommended dose for my pool along with 2 quarts of purple stuff. A bit Skeptical i put off the project for about a week or so until the wife began nagging me. After lowering the PH, i add the products. WOW! a bit of Hope, while adding The Scale and Copper Stuff i noticed as the powder makes contact with the plaster it instantly turned to Brite white removing the brown calcium buildup until it completely disolved. I continue to brush every morning and run the filter pump as normal. i'm on day 5 now and every morning my plaster looks whiter. I intend to continue treatment for the next 9 days to completely remove all scales.So Far, this has been the best $250 i've spent all year.

[mbar]

Is the product by "Jack's Magic"? They are very good and know a lot about stains:D I am glad to hear that this product works. "Jack's Magic" products are very good - although somewhat expensive. Keep us informed:)

[waterbear]

Jack's magic products are excellent. The stain solution 2 does drop the pH and you are, in effect, doing a no drain acid wash. United Chemical also has a no drain acid wash kit that is supposed to be very effective on scale desposits.

[thomas_CT]

Is the product by "Jack's Magic"? They are very good and know a lot about stains:D I am glad to hear that this product works. "Jack's Magic" products are very good - although somewhat expensive. Keep us informed:)
Yes it is.

[PoolNewbie2006]

Since you were all so quick to respond to my questions, I figured I should give an update on what helped me. Dropping the pH level really helped soften up a lot of the scale. When I went into the spa a couple days after keeping the pH down, some of the scale came right off using my bare hand. There were some trouble spots. For those, I purchased a stainless steel pot scrubber from the market and went to work. The seating areas in the pool, which I was most concerned about, is now as smooth as new. There are still some rough spots on the floor which I'll get to another time but I'm not too concerned. Provides some traction so not completely a bad thing.

One drawback of the stainless steel scrubber was that small pieces started to break off after heavy use. Being that I have dark plaster, it was hard to see the pieces and I'm sure some went into my filter. Now to clean out my filter, which is overdue anyway.

[waterbear]

Next time, instead of a stainless steel scrubber get a pumice stone at the pool supply. They work really well at removing scale.

[MaryS]

Would the "Jack's Magic" product be safe on dark plaster?

[mbar]

I am not sure, I would check with Jack's Magic - they have a great customer support staff.

[Lenny]

Anyone have an idea how low you should drop the PH before trying to physically remove scale?

[pairadocs]

Anyone have an idea how low you should drop the PH before trying to physically remove scale?

I'd love to know the same thing? I've heard 6.8 - 7.0 pH for scale brushing.

Bob

ps. Lenny, we're neighbours. I'm in Newark, DE

[steveinaz]

I have this same odd staining. It doesn't react to any of Magic Jacks metal testing, chorine does nothing to it, nor does vitamin C. It looks like light dirt staining or something. I even tried my stainless brush---NOTHING, stain doesn't move.

Which Magic Jack's product are you guys using?

[waterbear]

I have this same odd staining. It doesn't react to any of Magic Jacks metal testing, chorine does nothing to it, nor does vitamin C. It looks like light dirt staining or something. I even tried my stainless brush---NOTHING, stain doesn't move.

Which Magic Jack's product are you guys using?

Scale will not respond to sequestration or to vitamin c. It responds to acid washing and sandblasting.
The Jack's magic stain and scale stuff is, essentially, a no drain acid wash and requires that the heater be isolated and the pool closed for several weeks while it works. since it drops the pH quite low. if it is in isolates areas you can try a pumice stone. If on the waterline or tile you can drop the water a bit and try muriatic acid.