I currently live in Spain. I have a 5X10 m pool with a zodiac sals system. I recently drained it and had it completely regrouted. Now there is A LOT of black mould or algae appearing on all surfaces of the pool. I have been brushing it vigorously and eventually I can clear a lot of this away, but it reappears faster than I can brush it. I also feel that I am possibly or probably brushing away the grout with this. I have added MORE salt and this doesn’t appear to help. The water now tastes noticeably of salt. I don’t know if my salt cell is working efficiently or not. the salt system is approximately 3 years old. I do not cover it often during the sunny season. I am seeking ANY help or advice here. The PH fluctuates between 7.2 and 7.7 at the moment. Has anyone got any advice for me to try ? Thanks in advance
Mold or algae in my salt water pool
- Thread starter Starfly
- Start date
Welcome to TFP.
You have to raise your free chlorine (FC) level to kill the algae. It is best to use an alternative chlorine as your salt system will not be able to go higher enough to kill the algae. Do you have access to liquid chlorine as that is the quickest way to increase the FC in your pool.
Do you use stabilizer in your pool? This is the CYA level. If so, what is that reading in ppm?
We use the SLAM Process to kill algae. You must be able to test you pool water and also be able to add chlorine to raise your FC levels and then maintain those levels for a undetermined time to kill the algae.
You have to raise your free chlorine (FC) level to kill the algae. It is best to use an alternative chlorine as your salt system will not be able to go higher enough to kill the algae. Do you have access to liquid chlorine as that is the quickest way to increase the FC in your pool.
Do you use stabilizer in your pool? This is the CYA level. If so, what is that reading in ppm?
We use the SLAM Process to kill algae. You must be able to test you pool water and also be able to add chlorine to raise your FC levels and then maintain those levels for a undetermined time to kill the algae.
- Jun 24, 2021
- 15,872
- Pool Size
- 29000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- CircuPool RJ-60 Plus
You need a proper test kit to follow the SLAM process and test higher FC levels.
You can get one here in Spain...
piscinasyproductos.es
You can get one here in Spain...
Taylor K-2006 multiparametric analyzer test kit
Multiparametric test K-2006 of the Taylor brand, for the determination of various chemical levels of the water, very appropriate for the care of pools of any size. This analyzer kit is especially indicated for when a very precise measurement of the level of free chlorine is necessary, since the...
piscinasyproductos.es
You may already know this but I bring it up just in case. A salt water pool isnt sanitized by salt, it’s sanitized by chlorine. Lots of folks are mistaken about there not being chlorine in a salt water pool. The machine just turns the salt into chlorine with electricity. So do your best to get some chlorine in the water to kill the algae. Are good test kits available where you are in Spain?
thank you for all your assistance. I am very new at this and appreciate ALL help and advice. First the basics...
1) Free Chlorine ? I'm not sure what exactly this is. I understand that my salt cell will generate chlorine using electricity to activate the salt. My logic says that if I have the right amount of salt in my pool then the Chlorine levels will be correct.
2) SLAM. I have used a tub of something the shop recommended to me for shock. It cost me 27 euros and within 24 - 36 hours most of the algae had disappeared from the grouting in the pool.. BUT 24 hours later it has started to return.
3) my pool is in full sunlight at about 35 - 40 degrees ALL day. I covered it overnight when I used the shock powder and it looked so much better but when I left the cover off overnight following the successful treatment was when I noticed that the black mess in the grouting had begun to return.
4) I haven't asked about liquid chlorine here yet. most of the chlorine sold in the shops is in tablet or powder form. would that be suitable ?
5) I am not sure what exactly Cyanuric acid is or if I can buy it in pool shops in Spain.
6) there are basic test kits here for PH Chlorine and Salt but I haven't seen anything more sophisticated yet.
It sounds as though my salt cell isnt coping with the demands of tjhe pool and the environment. The water here is particularly hard water and in Spain it is called irrigation water. ie: not suitable for drinking and possibly doesn't contain any of the chemicals such as fluoride that is normally added to drinking water.
I feel that I really am missing something... ( possibly missing LOTS of things)
1) Free Chlorine ? I'm not sure what exactly this is. I understand that my salt cell will generate chlorine using electricity to activate the salt. My logic says that if I have the right amount of salt in my pool then the Chlorine levels will be correct.
2) SLAM. I have used a tub of something the shop recommended to me for shock. It cost me 27 euros and within 24 - 36 hours most of the algae had disappeared from the grouting in the pool.. BUT 24 hours later it has started to return.
3) my pool is in full sunlight at about 35 - 40 degrees ALL day. I covered it overnight when I used the shock powder and it looked so much better but when I left the cover off overnight following the successful treatment was when I noticed that the black mess in the grouting had begun to return.
4) I haven't asked about liquid chlorine here yet. most of the chlorine sold in the shops is in tablet or powder form. would that be suitable ?
5) I am not sure what exactly Cyanuric acid is or if I can buy it in pool shops in Spain.
6) there are basic test kits here for PH Chlorine and Salt but I haven't seen anything more sophisticated yet.
It sounds as though my salt cell isnt coping with the demands of tjhe pool and the environment. The water here is particularly hard water and in Spain it is called irrigation water. ie: not suitable for drinking and possibly doesn't contain any of the chemicals such as fluoride that is normally added to drinking water.
I feel that I really am missing something... ( possibly missing LOTS of things)
That’s not how it works. You need to measure the chlorine level and adjust the amount of time the salt cell is running to either add or reduce chlorine. The salt content doesn’t affect how much chlorine the device makes. If the salt runs low, it’ll stop making chlorine and if it gets too high it’ll stop making chlorine. All other times it makes the same amount of chlorine while it’s powered on.
Have you never measured chlorine levels in the water? That’s really your first step in getting it under control.
Are you able to purchase a test kit made by Taylor Technologies in Spain? It would be model K-2006C - the “C” relates to the size of the bottles for the reagents in the test kit. ”A” is the smaller bottle and “C” is the larger bottles.
You must be able to measure free chlorine and other levels. Please read Pool Care Basics for basic understanding of all chemicals and tests used for pool maintenance.
You must be able to measure free chlorine and other levels. Please read Pool Care Basics for basic understanding of all chemicals and tests used for pool maintenance.
You aren’t wrong in that salt is a necessary ingredient for the salt cell to produce chlorine, but if your cell isn’t producing enough chlorine for the pool, then you have a problem with the cell - either it isn’t running long enough, or it is nearing the end of its life, or it is coated with mineral deposits that are keeping it from making contact with the water.
This assumes that the salt content of the water is where it needs to be, and to know that, you need a salt test kit.
This assumes that the salt content of the water is where it needs to be, and to know that, you need a salt test kit.
okay so... first of all thank you to everyone who has responded to me so far. I have gone back to basic calculations and I have a pool that measures 10mx5xx3m ( 124cm at shallow end with 184 cm at deep end and a gradual slope with no steps or shelf ) I have calculated that this is 150,000 litres. Are my calculations correct ? I am awaiting a delivery of salt test strips and another set of strips that test for Free Chlorine, PH and Alkalinity. I have visited my local pool shop and they do indeed sell Liquid Chlorine which I shall buy soon. He also told me I need PH Reducer. he didn't understand what Cyanuric Acid was, maybe that is just my crappy Spanish but I am sure Amazon can bring me some. He told me I should use something called SAL FUMANT which appears to be Hydrochloric Acid. Google tells me "Hydrochloric acid is an aqueous solution of hydrogen chloride gas". as all the Spanish use it in their swimming pools. This is common apparently. A friend of mine said NOT to pour it in the pool as although it will make the water clear, it will also degrade my grouting and cause me problems with that. So, just use it to clean the salt cell and then rinse will before refitting it. Has anyone got any thoughts on my next attempt to start understanding and treating my pool ? Will those test strips be accurate enough for me and is there something else I need to check? I looked into getting the test kit recommended by this site but it will cost me 169 euros here in Spain. that's over a quarter of my pension hahaha
- Jun 1, 2018
- 16,000
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Cya (cyanuric acid) is sold separately here in the United States in liquid & granular form but it is also inside of Trichlor & dichlor chlorine products. To ensure you are using the correct amount of chlorine to sanitize your pool for maintenance & to eradicate algae you must know the current cya level.
Have you used any dichlor (Dichloro-S- Triazinetrione)
or
Trichlor (Trichloro-S-Triazinetrione)
products in your pool since refilling? Tablets or powders? If so, how much?
Yes, The test kit is pricey but it is the key to solving your problem & preventing it from recurring in the future. Without accurate data you’re flying blind which is also quite costly.
While your friend is trying to be helpful, he is mistaken,
Hydrochloric acid is muriatic acid & should be used to control ph it does nothing to make the water clear or sanitize. You need liquid chlorine for that.
If poured slowly infront of a return jet away from the pool’s wall it is perfectly fine to use. Brush the area afterwards.
If you have any spills clean them up immediately.
Dry acid should not be used as it adds sulphates to the water which does have the consequences your friend mentioned.
Cleaning your cell with acid should be a last resort & even then it should be heavily diluted (4:1) as it removes the coating from the plates that produces the chlorine thereby reducing the cell’s life. If the cell has visible scale (which is the only time you should clean it) try 1st using a popsicle stick/credit card (not something metal) to remove it or strong blasts from the hose. Before progressing to diluted vinegar then lastly diluted acid.
Until you have data (test results) to work with you should add 5ppm worth of liquid chlorine (sodium hypochlorite) to the water each day to keep things from getting worse.
150k liters is roughly 40k gallons
Use PoolMath to calculate amounts based on your chlorine strength & pool volume.
If it is 10% strength that is 2 gallons.
Have you used any dichlor (Dichloro-S- Triazinetrione)
or
Trichlor (Trichloro-S-Triazinetrione)
products in your pool since refilling? Tablets or powders? If so, how much?
Yes, The test kit is pricey but it is the key to solving your problem & preventing it from recurring in the future. Without accurate data you’re flying blind which is also quite costly.
While your friend is trying to be helpful, he is mistaken,
Hydrochloric acid is muriatic acid & should be used to control ph it does nothing to make the water clear or sanitize. You need liquid chlorine for that.
If poured slowly infront of a return jet away from the pool’s wall it is perfectly fine to use. Brush the area afterwards.
If you have any spills clean them up immediately.
Dry acid should not be used as it adds sulphates to the water which does have the consequences your friend mentioned.
Cleaning your cell with acid should be a last resort & even then it should be heavily diluted (4:1) as it removes the coating from the plates that produces the chlorine thereby reducing the cell’s life. If the cell has visible scale (which is the only time you should clean it) try 1st using a popsicle stick/credit card (not something metal) to remove it or strong blasts from the hose. Before progressing to diluted vinegar then lastly diluted acid.
Until you have data (test results) to work with you should add 5ppm worth of liquid chlorine (sodium hypochlorite) to the water each day to keep things from getting worse.
150k liters is roughly 40k gallons
Use PoolMath to calculate amounts based on your chlorine strength & pool volume.
If it is 10% strength that is 2 gallons.
Do NOT use the acid to clean your salt cell. It will wear the precious metals off of the plates and reduce its lifespan.
You SHOULD use that acid to reduce the pH of your water if it’s over 8.0. But you don’t need to reduce the pH unless it’s over 8.0
Unfortunately the test strips aren’t worth much in terms of accuracy. Are they better than nothing at all? Probably. But beware that they may lead you to spend money on other stuff you don’t need.
The CYA is also called chlorine stabilizer. Maybe that’ll help.
originally it was stated that the pool was 5x10 m which is 50 sq m. This latest posts indicate it may be an L shape. 10x5x3m
I used an average depth of 1.54m
So using 10x5x1.54 meters which converts to 32.8x16.4x5.05 ft - which is 2717 cu ft which converts to 20,300gals or 76,843 liters. So that is half the size that was originally calculated. Just want to ensure we are using the correct volume when recommending volume of chemicals to use.
Please confirm what the layout of the pool is - rectangular or is it truly "L" shaped (then we need more data to do proper calculations). Show a layout or a picture of the pool.
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thank you all so far for all the help and advice you have given me. I have received my test kits and have included a photo of them so you can assess what I am using.
The test came out as follows.
Free Chlorine 5
PH 6.8
Total Alkalinity 0
Salt 7020ppm
okay I TRIED to include the photo but it doesn't seem to work.. slow internet maybe but they are called AQUACHECK Pool and Spa test strips
anyway I'm guessing here that my salt level is too high, the Total alkalinity is way to low.... PH is too low ( I think that ought to be 7.2 - 7.4 ) , and free chlorine ? I'm not sure but probably too low as well. I would love now some advice to correct these readings and hopefully not overcorrect them...
The test came out as follows.
Free Chlorine 5
PH 6.8
Total Alkalinity 0
Salt 7020ppm
okay I TRIED to include the photo but it doesn't seem to work.. slow internet maybe but they are called AQUACHECK Pool and Spa test strips
anyway I'm guessing here that my salt level is too high, the Total alkalinity is way to low.... PH is too low ( I think that ought to be 7.2 - 7.4 ) , and free chlorine ? I'm not sure but probably too low as well. I would love now some advice to correct these readings and hopefully not overcorrect them...
Attachments
Last edited:
- Jun 1, 2018
- 16,000
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Unfortunately the strips are pretty unreliable.
it also doesn’t sound like they measure cya - hence the need for a proper drop based kit.
You must know your cya/stabilizer level to properly chlorinate as you can see in the charts I posted above.
Trichlor & dichlor powders & tablets contain cya - it doesn’t leave the water unless you replace the water - have you used any of these?
If so how much & which ones?
Understand that Most strips bleach out at the fc levels needed for the SLAM Process giving false results.
If you are to believe those limited results you need 40ppm worth of baking soda (sodium bicarbonate) to get the TA up now & point your jets up to aerate the water to help increase ph.
Use PoolMath to calculate amounts.
That seems like alot of salt- what are the salinity requirements of your swcg?
it also doesn’t sound like they measure cya - hence the need for a proper drop based kit.
You must know your cya/stabilizer level to properly chlorinate as you can see in the charts I posted above.
Trichlor & dichlor powders & tablets contain cya - it doesn’t leave the water unless you replace the water - have you used any of these?
If so how much & which ones?
Understand that Most strips bleach out at the fc levels needed for the SLAM Process giving false results.
If you are to believe those limited results you need 40ppm worth of baking soda (sodium bicarbonate) to get the TA up now & point your jets up to aerate the water to help increase ph.
Use PoolMath to calculate amounts.
That seems like alot of salt- what are the salinity requirements of your swcg?
Almost guaranteed those results are chemically impossible unless you filled the pool with distilled water.
I would not make any recommendations based on these readings using test strips. The results are unbelievable unless you dumped a ton of salt in the pool to raise the salt level and acid to lower TA and pH.
You need a proper drop kit such as Taylor Technologies K-2006.
Also, please confirm your pool dimensions as not sure we are dealing with a 20k gal pool or a 40k gal pool.
it does seem like a lot of salt and the fault is all mine.. I didn't understand how much salt to add. I bought 25kg bags of salt and added.. then tested... then added and tested... until the testing came out okay... however..... the salt content ppm kept rising so the fault was with my testing I have been working to rectify that by means of backwashing and rinsing... and adding clean water..... bringing it down slowly.... I am learning that slowly is better than trying to do things quickly.
I am now trying to raise the PH slightly.. it is currently 7.11 - 7.12 and I believe that I can add sodium bicarbonate or baking soda to bring it up. I have used the calculator here and discovered that I have approximately 16.000 gallons in my pool Can you advise me on how to raise the PH slightly to bring it to somewhere between 7.2 and 7.8.
I have now received CYA test strips and it indicates that It is zero. I have located a local supplier that can sell me stabilizer but I don't really know what quantity to add to raise this . I'm starting to understand that the CYA will help prevent the chlorine from being destroyed by the sun but I am pretty sure that its possible to add TOO MUCH stabilizer . I hope you can correct me or advise me on anything I have got wrong or have overlooked.
I am nearly 70 years old... I forget a lot of stuff I learn and get confused sometimes but this is making sure I refer constantly to TFP and the information on here. Next time I am going to get a place with a communal pool and let some other person manage it hahaha
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Your pH is just fine at 7.1. It will rise on its own over time.
The CYA can definitely become too much. Ideally you’de have 30-50ppm. Are you able to use the poolmath app? It has a calculator for additions. But I’m not so sure how useful it is with CYA test strips. My experience with strips has been pretty bad.
- Jun 1, 2018
- 16,000
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
If your ta is 50 or above you don’t need to do anything to raise ph besides aeration which you can do by pointing the jets upwards, running water features or simply by using the pool & splashing around.
Any ph in the 7’s is fine.
For cya - you want 30ppm worth
PoolMath will calculate the amount for you based on your pool volume.
If it is granular then add the prescribed amount to a sock
& hang it in front of a running return away from the pool wall. Give the sock a squeeze every now & then to help dissolve the cya. It is fine to be in the pool when you do this.
You may need to split the dose between multiple socks as in my experience a regular crew/tube or skimmer sock will hold about 2# worth comfortably.
Any ph in the 7’s is fine.
For cya - you want 30ppm worth
PoolMath will calculate the amount for you based on your pool volume.
If it is granular then add the prescribed amount to a sock
& hang it in front of a running return away from the pool wall. Give the sock a squeeze every now & then to help dissolve the cya. It is fine to be in the pool when you do this.You may need to split the dose between multiple socks as in my experience a regular crew/tube or skimmer sock will hold about 2# worth comfortably.
- Jun 1, 2018
- 16,000
- Pool Size
- 26000
- Surface
- Vinyl
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
While the addition of cya (if you truly currently have zero) will help with the sun consuming your chlorine it won’t do anything about the algae.
For that you need to do the
SLAM Process with liquid chlorine.
To do that accurately & efficiently (in terms of time, energy & expense)
you really do need the fas/dpd test as it tests higher fc levels accurately unlike strips or the yellow OTO drop test.
Otherwise you are truly flying blind.
It is not a one time addition of chlorine- it is MAINTAINING slam level fc for your cya until you pass ALL 3 end of slam criteria as listed in the article.
FC/CYA Levels
Your swcg is not capable of overcoming an algae problem- they are simply designed to maintain normal daily fc losses in the 2-5ppm range.
For that you need to do the
SLAM Process with liquid chlorine.
To do that accurately & efficiently (in terms of time, energy & expense)
you really do need the fas/dpd test as it tests higher fc levels accurately unlike strips or the yellow OTO drop test.
Otherwise you are truly flying blind.
It is not a one time addition of chlorine- it is MAINTAINING slam level fc for your cya until you pass ALL 3 end of slam criteria as listed in the article.
FC/CYA Levels
Your swcg is not capable of overcoming an algae problem- they are simply designed to maintain normal daily fc losses in the 2-5ppm range.