Brown stains spreading

[cmcq]

We have a 22k gallon IG gunite pool with a mineral springs SWC. This is the 2nd year of operation. We opened 2 weeks ago and everything went well, except some of the stains we accumulated over the winter didn't go away. I assumed they were from leaves b/c they were mostly on the steps and love seat, but now there is some discoloration to the bottom and the face of the steps. The darkest spots are brown and are about the size of a one dollar coin, but the spreading is more of a light brown coating spreading around the stains.

I tried Ph down crystals on one or two, figuring that was the same as concentrated muriatic acid, but it didn't work. I also tried directly placing a little shock on the spot and it seemed to lighted over a few days but didn't work entirely and I don't need/want that much chlorine in the pool all the time.

This a.m. I tried crushed Vitamin C tablets directly on the stains and it worked, so based on what I've read here it would seem to be a metal problem. (not sure where the metal would have come from b/c I had no probs last year and the fill water this year was 95% rain/snow from the winter and 5% hose water, which is what I used for about 20% of the water last year, but how it got here isn't really the issue.

Readings are:

FC = 12
TC = 12 (is that possible/correct? I took it twice so I think it is accurate, but that doesn't seem good)
Ph 7.2
Alk = 100 (earlier this week I added 4 lbs baking soda b/c alk had been too low)
CYA = 70
Temp = 72

I added 200 lbs salt last week as the mineral reading on the SWC was 1300. That reading is now at 3000, but I've turned it off due to the high clorine rating.


So, what do I do about the stains, and am I correct that the chlorine it way too high?

Thanks

[mbar]

Your chlorine is not too high. According to the "best guess chart" that we use, with the cya 70, your chlorine at 12ppm is good, a little high but as you can see it doesn't even come near shock level. You can run your pool at about 8ppms.

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

All of your numbers seem to be in range, but you didn't post your calcium levels.

As for the stains, I would try putting in a sequestering agent first - something like sequasol, or jack's magic, or metal free. Put in enough per the directions on the bottle. A little extra won't hurt, but not enough will keep some metals free to precipitate out of the water. Keeping your ph low, 7.2 is ok, but no higher. Let your pump run 24/7 for a while and see if the stains get any lighter. If they don't let me know. Then you can do a regular stain treatment. As for where did the metals come from? I don't know, but since they are in there you need something like the sequestering agent to keep them in suspension.

[gregugadawg]

take a water sample to your local pool store and tell them you need stain remover. Be sure you use a metal remover when you add the stain remover as well. This is going to work since the vitamin c worked on the stains. You will however need to lower the chlorine level to less than 1 before treating the stains.

[waterbear]

I would say Marie is right on the money. She is pretty much the expert on stain treatment around here

Brown stains are usually caused by iron. Might be intersting to get your water checked but then again, once the stain has formed the metal is no longer IN the water, unless it is a recurring problem such as your fill water.

[cmcq]

I added a Metal, Stain and Scale Out product, have run the pump and brushed the stains but there hasn't been a change in their appearance. During this period, the PH rose so I treated with muriatic acid to bring back down. Any suggestions on what to do next?

[mbar]

You will probably have to do a stain treatment. You are using a product that is probably a sequestering agent - it will bind with the metals that are suspended in the water, but if the stains are embedded, they will not lift off with just the sequesterant. You can get ascorbic acid which is vitamin C, or there are other products that use oxcylic acid? I am not sure if that is the right spelling. I always use the ascorbic as it is the most mild. Here is a link to buying it cheaper than the regular pool products.

http://www.msm-msm.com/store/agora.c...scorbic%20Acid

http://www.chemistrystore.com/Ascorbic_Acid.htm

If you chose to do this treatment, I can give you directions on how to use it.

[blk133]

How much of Vitamin C would one need for a 35000 G. in-ground fiberglass pool?

I am not even sure that I have a metal stain, just some kind of stain is there on the floor and on walls I start to see a patern of how they applied a paint with a roller.

Thanks,
B.

[tmmort]

...
If you keep the pH between 7.2 - 7.4 (it keeps the metals in solution) you should not have too many stain problems. Keep the REAL alkalinity between 90 and 100, this to helps keep the metals from falling out of solution, using your CYA number to adjust this. Example a CYA of 60 X ph 7.4 adjustment of .33 gives a reading of 19.8. So your alkalinity should read 120 on your test kit to get a real alkalinity of 100.2. At a CYA of 40 the adjustment is 40 X .33 or 13.2 so your reading should be around 110 to get a real count of 96.8.
...

I've never heard of this relationship between CYA/pH/TA. Can you elaborate and/or post link that explains this? Thanks!

[smallpooldad]

Firstly if you do not have a pool sweeper with brushes you will need to do a lot of brushing while all this is going on. The fact that your pool is at 72 F is beneficial to the chlorine as it is stronger at lower temperatures.

One reason that you may be getting stains is your REAL alkalinity could be too low for a vinyl pool, if you are not adjusting it, please see below.

You can buy vitamin C POWDER from your local health store DO NOT GET the crystals they will not work as they are non-acidic.

You will need 1 to 1 1/2 lbs per 10,000 gals. Keep the pH low, say 7.0 and sprinkle it around the wall. I did mine at a pH of 6.0 in a gunite pool and it worked very well but a number of persons on this website think that 6.0 is far too low, although ascorbic acid has a pH 6.0; at 7.0 I had limited success.

VERY VERY important drop the chlorine to 0, yes zero, before putting the the vitamin c (ascorbic acid) into the pool, or all the the acid will do is eat up the chlorine and not do the work on the stain. You can buy a chlorine reducing chemical from your local pool store. Sprinkle the powder around the walls or near the stains.

If you are worried about an algae bloom put in one quart of Algaeside 60, not 50, 40 or 30 per 10,000 gals. Then immediately add 3 quarts per 10,000 gals of metal or stain treat (not stain removal) to catch the metal stain in solution.

In regards to the filter adding DE helped catch more particles, then again this may be more in the mind than in reality. With a 300 lb sand filter (9,000 gal pool) add enough DE, through the skimmer box, to raise the pressure by 1, this is about 3 cups, add one cup at a time and wait 15 to 20 minutes. Once you have started the ascorbic acid process you may notice, if you have a sand or small filter, the pressure rising dramatically and your filter slowing down. I back washed for 1 minute only after each of the first two 12 hour periods as the filter became blocked.

It is best to first backwash and then COMPLETELY DRAIN the pool after having run the pump for 48 hours non-stop. If you do not the metal will eventually fall out of solution and cause the stains to reappear via deposit.

Refill and bring the calcium hardness up to at least 200 - 250 for gunite, 100 to 150 for vinyl. I think the higher number works better with stain problems although I am not sure why. Some members have suggested that calcium in the filter helps get the metals deposited in the filter and then washed out in the backwash.

Once you refill it is a good idea to shock your pool first with liquid bleach 20 ppm (Ultra Bleach from Walmart is cheap) at a low pH of 7.2 then after 48 hours bring your pool back into balance and FINALLY add 1 quart per 10,000 gals metal out to keep any metal introduced into pool with the new water in solution. Do this once a month, or as Mbar suggests a little say 3-4oz if the stains reappear.

DO NOT SHOCK if you are not refilling the pool. However if you do not drain and refill you will have the ascorbic acid in solution which will eat the chlorine in large doses. It will take lots and lots of chlorine before you can maintain a stable level. This may take 2-5 days of constantly adding chlorine, a real pain.

If you keep the pH between 7.2 - 7.4 (it keeps the metals in solution) you should not have too many stain problems. Keep the REAL alkalinity between 90 and 100 for gunite, 100 to 120 for vinyl, this also helps keep the metals from falling out of solution, using your CYA number to adjust this. Example a CYA of 70 X ph 7.4 adjustment of .30 gives a reading of 21.0. So your alkalinity should read 120 to get a real alkalinity of 99.0. At a CYA of 40 the adjustment is 40 X .30 or 12.0 so your reading should be around 110 to get a real count of 98.0.

ph CyF adjustment

6.5 0.11
7.0 0.22
7.2 0.26
7.4 0.30
7.6 0.33
7.8 0.35
8.0 0.36
8.5 0.38

If your CYA is 70 then you should keep the Total Chlorine between 7-8. Remember it takes 3-5 days for CYA reading to measure correctly as it dissolves very slowly, so do not add more than is necessary.

Do not shock the pool after you are in balance for at least 2 weeks or it may go cloudy. Add Algaecide 60 if you like.

I learnt most of this from Mbar so you have her to thank.

Finally, two finallys, first if you have blackish looking stain streaks these are normally caused by tannin from leaves, to dissolve these you would need to keep the chlorine up at around 30 ppm for 48 to 72 hours. Carefully monitor your pH level to 7.2 and Your REAL alkalinity to 90-100 for gunite, 100 to 120 for vinyl. Running your pump the entire time. Second, you may still need to do the the muriatic clean process but this is more difficult and should only be used as a last resort, I think doing the ascorbic acid process at a pH of 6.0 is better and less dangerous than putting a muriatic mix of say 1 part acid to 3 or 4 parts water directly onto the wall but once again some members may disagree and I have no experience of vinyl pools.

Aloha and good luck.

[smallpooldad]

Cyanuric Acid Correction To Total Alkalinity.

The following is taken from Taylor's "Pool and Spa Water Chemistry" (rev 9/94).

"Total alkalinity is a measurement of both carbonate alkalinity and cyanurate alkalinity present in a sample. Since water balance calculations only use the carbonate alkalinity portion, a a correction (which varies with pH) should be applied to compensate for the cyanurate portion."

They further state: "Note: While Taylor Technologies recommends using the correction, some industry professionals remain skeptical and question its value."

It works for me I seem to have far less variation on a daily/weekly basis if I use the adjustment.