Apparently ‘permanent’ algae stains

[Gasolina]

Hi,
I have had no problems with my pool for some years with all your help and advice. Sadly, this autumn, having been away for a couple of months, we have algae stains which are impossible to remove by brushing. Unfortunately, the guy looking after the pool, just threw chlorine at it - 50 litres of 14% liquid bleach.
We have very hard water with a high iron content and so have a water filtration system for the house.
My readings are:
FC 1.5555 ( he put the bleach in a few days ago )
PH 8.0
CYA 45
Calc 180
Total Alkalinity 120
It is an in ground liner pool. Temperature 20 C
Please could anyone give me some ideas, as at the moment I have the awful feeling I am going to have to get a new liner.
Fingers crossed and thank you in advance.
Caroline

 

[Texas Splash]

I know you say the stains are algae (organic), and perhaps they are. But I would still try the following:
1 - Rub a Vitamin C tablet on the stain to see if it's iron
2 - If you have any dry acid (pH Down), you can try placing some of that in a thin sock or nylon and rubbing it on the stain as well (copper)
3 - Your calcium level seems to be low, so I wouldn't think it could be calcium staining, but it depends on the accuracy of your testing.
4 - If none of those work and the staining is confirmed as organic that only just occurred in the past couple months, it will take time. Time for the elevated chlorine level to penetrate the stains and lift them. Above you list an FC of 1.5555 (?) which is an odd number to see. But with a CYA of about 50, you could easily increase the FC to 20 (SLAM level) and see if that helps. Maybe keep the FC between 10 - 15 for a week or so as well.

Testing accuracy is the other factor in all of this. Makes a world of difference when trying to isolate a true cause.

 

[Mdragger88]

Here’s some info about stains & how to identify them

Stains in Your Pool

The stained pool is beyond embarrassing. Our in-depth Guide to remove stains in your pool will help you to remove the stains and prevent them in the future.

www.troublefreepool.com

Your fc is quite below minimum for your cya - your target is 6-8 ppm.
following the FC/CYA Levels is how you prevent algae. You may still have an algae problem if a SLAM Process wasn’t properly preformed.
Doing an Overnight Chlorine Loss Test can rule out whether or not you still need to slam. Then you can deal with the staining.

 

[Gasolina]

I know you say the stains are algae (organic), and perhaps they are. But I would still try the following:
1 - Rub a Vitamin C tablet on the stain to see if it's iron
2 - If you have any dry acid (pH Down), you can try placing some of that in a thin sock or nylon and rubbing it on the stain as well (copper)
3 - Your calcium level seems to be low, so I wouldn't think it could be calcium staining, but it depends on the accuracy of your testing.
4 - If none of those work and the staining is confirmed as organic that only just occurred in the past couple months, it will take time. Time for the elevated chlorine level to penetrate the stains and lift them. Above you list an FC of 1.5555 (?) which is an odd number to see. But with a CYA of about 50, you could easily increase the FC to 20 (SLAM level) and see if that helps. Maybe keep the FC between 10 - 15 for a week or so as well.

Testing accuracy is the other factor in all of this. Makes a world of difference when trying to isolate a true cause.

Thank you for your advice. I realise the FC was very low, but because of the problem decided to test first as I knew I should have to shock the pool. I will get some Vitamin C tomorrow and try it. I have some muriatic acid which I could try on one of the corners of the pools steps. I know that testing is the most important thing. Unfortunately in Europe we can no longer get the good American test kits. I have been using an FAS-DPD kit for the past few years but ran out and could only get a small Taylor Bromine kit. It is so frustrating as I was really particular at testing daily at the same time. If it is iron, is there a product like vitamin C made on a large scale for combatting the stains, although I am a bit confused, as we have managed with the same iron heavy water since we built the pool 10 or so years ago. Anyway, will try all and test again in the morning

 

[Gasolina]

Here’s some info about stains & how to identify them

Stains in Your Pool

The stained pool is beyond embarrassing. Our in-depth Guide to remove stains in your pool will help you to remove the stains and prevent them in the future.

www.troublefreepool.com

Your fc is quite below minimum for your cya - your target is 6-8 ppm.
following the FC/CYA Levels is how you prevent algae. You may still have an algae problem if a SLAM Process wasn’t properly preformed.
Doing an Overnight Chlorine Loss Test can rule out whether or not you still need to slam. Then you can deal with the staining.

Hi,
Thanks for your advice. When I arrived and saw the problem, I knew I should have to shock the pool anyway, so tested straight away. Realised that fc was very low. Assumed that the guy who looks after the pool had put all the chlorine in a few days ago, when he realised there was a problem, and as we have cya pf 45 it would not have stayed in the water for long. I think he panicked.
What is an OCLT please?

 

[Mdragger88]

Perform the Overnight FC Loss Test (OCLT)

The Overnight Chlorine Loss Test tells if the SLAM is finished or if you need to start a SLAM. This article says how to do the OCLT.

www.troublefreepool.com

 

[Mike1162]

If it is iron, is there a product like vitamin C made on a large scale for combatting the stains

ascorbic acid

 

[Gasolina]

Hi,
Thanks for your advice. When I arrived and saw the problem, I knew I should have to shock the pool anyway, so tested straight away. Realised that fc was very low. Assumed that the guy who looks after the pool had put all the chlorine in a few days ago, when he realised there was a problem, and as we have cya pf 45 it would not have stayed in the water for long. I think he panicked.
What is an OCLT please?

Thank you. Will do the OCLT test tonight.

 

[Gasolina]

ascorbic acid

Thank you.

 

[Gasolina]

I know you say the stains are algae (organic), and perhaps they are. But I would still try the following:
1 - Rub a Vitamin C tablet on the stain to see if it's iron
2 - If you have any dry acid (pH Down), you can try placing some of that in a thin sock or nylon and rubbing it on the stain as well (copper)
3 - Your calcium level seems to be low, so I wouldn't think it could be calcium staining, but it depends on the accuracy of your testing.
4 - If none of those work and the staining is confirmed as organic that only just occurred in the past couple months, it will take time. Time for the elevated chlorine level to penetrate the stains and lift them. Above you list an FC of 1.5555 (?) which is an odd number to see. But with a CYA of about 50, you could easily increase the FC to 20 (SLAM level) and see if that helps. Maybe keep the FC between 10 - 15 for a week or so as well.

Testing accuracy is the other factor in all of this. Makes a world of difference when trying to isolate a true cause.

Hi again,
I have tried to test the staining with the only vitamin C tablets I could get ( effervescent ). I held it down on the staining and maybe it changed a bit, but didn’t disappear. Also tried some ph minus and again, maybe it changed a bit. I can’ t get ascorbic acid here, but can get citric acid. Could I use that? If so, what is the best way to use it as the staining is over large areas of the pool in both deep and shallow ends.
Thank you.

 

[Gasolina]

ascorbic acid

Hi,
I can’t get ascorbic acid here. I can get citric acid. Could I use that instead? If so, what is the best method as the staining is in large areas of the liner i. Both the deep and shallow ends.
Thank you.

 

[Mike1162]

Hi,
I can’t get ascorbic acid here. I can get citric acid. Could I use that instead? If so, what is the best method as the staining is in large areas of the liner i. Both the deep and shallow ends.
Thank you.

Below is a link on how to treat the whole pool. It does mention using citric acid instead of ascorbic acid. I'm not sure if it's worth trying if the vitamin C didn't remove the stain.

Ascorbic Acid Treatment - Further Reading

 

[Gasolina]

I know you say the stains are algae (organic), and perhaps they are. But I would still try the following:
1 - Rub a Vitamin C tablet on the stain to see if it's iron
2 - If you have any dry acid (pH Down), you can try placing some of that in a thin sock or nylon and rubbing it on the stain as well (copper)
3 - Your calcium level seems to be low, so I wouldn't think it could be calcium staining, but it depends on the accuracy of your testing.
4 - If none of those work and the staining is confirmed as organic that only just occurred in the past couple months, it will take time. Time for the elevated chlorine level to penetrate the stains and lift them. Above you list an FC of 1.5555 (?) which is an odd number to see. But with a CYA of about 50, you could easily increase the FC to 20 (SLAM level) and see if that helps. Maybe keep the FC between 10 - 15 for a week or so as well.

Testing accuracy is the other factor in all of this. Makes a world of difference when trying to isolate a true cause.

Hi again,
i did the

I know you say the stains are algae (organic), and perhaps they are. But I would still try the following:
1 - Rub a Vitamin C tablet on the stain to see if it's iron
2 - If you have any dry acid (pH Down), you can try placing some of that in a thin sock or nylon and rubbing it on the stain as well (copper)
3 - Your calcium level seems to be low, so I wouldn't think it could be calcium staining, but it depends on the accuracy of your testing.
4 - If none of those work and the staining is confirmed as organic that only just occurred in the past couple months, it will take time. Time for the elevated chlorine level to penetrate the stains and lift them. Above you list an FC of 1.5555 (?) which is an odd number to see. But with a CYA of about 50, you could easily increase the FC to 20 (SLAM level) and see if that helps. Maybe keep the FC between 10 - 15 for a week or so as well.

Testing accuracy is the other factor in all of this. Makes a world of difference when trying to isolate a true cause.

hi again,
I have done an OCLT test and am not losing chlorine overnight.
I have also retested everything, using new reagents where possible and have one very interesting different result. The Calcium Hardness is 360 ! Could that be the cause of the ‘permanent’ staining? Could it be reacting with dead algae and iron in the water? Any tips please? Will the stain become more difficult to remove if left overwinter? We are supposed to be leaving this week!
Thank you.

 

[Gasolina]

Here’s some info about stains & how to identify them

Stains in Your Pool

The stained pool is beyond embarrassing. Our in-depth Guide to remove stains in your pool will help you to remove the stains and prevent them in the future.

www.troublefreepool.com

Your fc is quite below minimum for your cya - your target is 6-8 ppm.
following the FC/CYA Levels is how you prevent algae. You may still have an algae problem if a SLAM Process wasn’t properly preformed.
Doing an Overnight Chlorine Loss Test can rule out whether or not you still need to slam. Then you can deal with the staining.

hi again,
I have done an OCLT test and am not losing chlorine overnight.
I have also retested everything, using new reagents where possible and have one very interesting different result. The Calcium Hardness is 360 ! Could that be the cause of the ‘permanent’ staining? Could it be reacting with dead algae and iron in the water? Any tips please? Will the stain become more difficult to remove if left overwinter? We are supposed to be leaving this week!
Thank you.

 

[Gasolina]

Below is a link on how to treat the whole pool. It does mention using citric acid instead of ascorbic acid. I'm not sure if it's worth trying if the vitamin C didn't remove the stain.

Ascorbic Acid Treatment - Further Reading

Thank you very much for the link to the really clear instructions.

 

[Texas Splash]

The Calcium Hardness is 360 ! Could that be the cause of the ‘permanent’ staining?

It should not as that's not a very high number at all. But two things could influence that though - the accuracy of your CH test and the pH level in the past. Even if the CH number is in a good position, if the pH gets too high, scale can occur. Scaling can present a dull, browning color, and can also cover organic staining.

 

[Gasolina]

It should not as that's not a very high number at all. But two things could influence that though - the accuracy of your CH test and the pH level in the past. Even if the CH number is in a good position, if the pH gets too high, scale can occur. Scaling can present a dull, browning color, and can also cover organic staining.

That is what we now think has happened. Whilst we were away, the PH level was allowed to get too high and scale has covered the algae and possibly some rust stains.
I have now lowered the ph substantially - to 7.0 ( is that low enough ?) and am aerating to try to lower the a TA to help stop the PH drifting upwards and am scrubbing the pool and changing the filters daily. If I make sure that the PH is kept low whist we are away, should the stains eventually disappear? If there are any iron stains left when we return, I will treat with ascorbic acid as by then we will have been able to source some. One thing worrying me - will the stains be harder to remove if they are left over winter? If so , we will have t come back sooner than planned. Really appreciate all your help.

 

[Texas Splash]

I have now lowered the ph substantially - to 7.0 ( is that low enough ?)

It might help. Be sure to use the PoolMath APP to track your "CSI" number. Four factors (pH, TA, CH, and water temp) influence the CSI, pH having the most immediate impact. You can try to keep the CSI negative (about -0.3 to -0.6 for a few weeks (maybe even months) along with brushing to see if that helps. Keep in mind lowering the CSI to make the water more aggressive isn't an exact (uniform) process, so it could impact plaster differently across the entire pool, so be sure to monitor all areas. But over time it may help to thin any scale and expose items underneath.

 

[PCR]

It might help. Be sure to use the PoolMath APP to track your "CSI" number. Four factors (pH, TA, CH, and water temp) influence the CSI, pH having the most immediate impact. You can try to keep the CSI negative (about -0.3 to -0.6 for a few weeks (maybe even months) along with brushing to see if that helps. Keep in mind lowering the CSI to make the water more aggressive isn't an exact (uniform) process, so it could impact plaster differently across the entire pool, so be sure to monitor all areas. But over time it may help to thin any scale and expose items underneath.

You mention plaster, but they said in the first post "I have the awful feeling I am going to have to get a new liner." so assuming the pool is a vinyl liner pool.

 

[Texas Splash]

You mention plaster, but they said in the first post "I have the awful feeling I am going to have to get a new liner." so assuming the pool is a vinyl liner pool.

Ugh. How did we miss that earlier? @Gasolina, please be sure to update your signature with all of your pool info. See mine as an example. We refer to that sig on each post. With a liner pool, remember that normally the CSI factors we discussed above would not apply to you (liner) "unless" there is indeed scale on the liner.

On another note, with a liner you might need to be sure the staining you are seeing isn't from something behind the liner itself. There are situations where that can happen as well.