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.c...scorbic%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