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Thread: Saltwater pool, can't get rid of algae

  1. #1

    Saltwater pool, can't get rid of algae

    I have a 25,000 gallon saltwater pool with a de filter. I live in Texas and the days are getting really warm (85-90 degrees), which is probably exacerbating the algae problem. My husband also uses the spa twice a day, which my pool company told me burns off the chemicals.

    I am fighting a losing battle with algae and need help. I have it on the walls and bottom of the pool and my pool vac just lost a wheel so I am waiting for a repair part on that - it still kind of runs, but certainly not like it should.

    I have a test kit that was given us by the pool company which reads as follows with my pool readings

    cl Free Chlorine - 1
    CL Total chlorine - 0
    ALK - 120
    PH - 8.0
    hard - 250

    I have been reading the posts and have seen some other abbreviations that are not listed on my test strips, so maybe I need to get different test strips?

    I have used a 198 oz container of bleach, for the past two days (one yesterday, one today). Before that my free chlorine was 0.

    Our pool is 3.5 years old and we had a pool company until November. I was convinced that I could take care of the pool myself and would like to do that, but need guidance.

    Do I need to shock the pool? How do I do that? I have been trying to brush the algae, but it seems to be growing exponentially and I can't keep up.

    I would appreciate any help. Thanks so much.
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  2. #2

    Re: Saltwater pool, can't get rid of algae

    Keep reading pool school.
    You need a drop based test kit. Tftests.net sells the TF100 that everyone raves about. I just got mine today..ordered it Monday. Very good service!

    You need to SHOCK but to know how much bleach you need to know your cya level. Play with the pool calculator. You enter your CYA level and it tells you what your target FC levels are for maintenance and shock and then it tells you how much bleach to add based on your readings and pool size. Lots of nerdy fun!

    You need to be able to test, to get your FC to shock value and keep it there until algae clears..and while at shock level filter filter filter, brush, vacuum, repeat. You do that until your water clears and your FC holds within 1 ppm overnight.

    CYA is also called "stabilizer" and if it's too low the sun will "burn up" all your chlorine. Too high and you your chlorine needs are so high you will have to buy stock in Clorox. You want it just right.
    Location: East TN
    ? 15x30 Lomart Above ground

  3. #3
    Mod Squad Butterfly's Avatar
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    Re: Saltwater pool, can't get rid of algae

    Hi agarza8543 and welcome to the forum!

    What cardiacmommy said

    Read Pool School! Big white button, top right on each page...read & read again.

    If your pH is 8, you should lower it to about 7.2- ish for now.

    Please read this pool-school/read_before_you_post and post the requested info.*

    Yep, you need a good test kit and you can read about the recommended test kits in Pool School. Link in my sig to TFTestKits - best bang for the buck, IMHO.

    Okay, *please post a full set of test numbers and let us know where/how you got them and tell us more about your pool/equipment.

    We will help you turn your pool into the sparkling clean oasis it should be
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

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  4. #4

    Re: Saltwater pool, can't get rid of algae

    Thank you for your replies! I appreciate your time and expertise so much.

    Follow up questions:

    I will definitely ordered the recommended test kits, but in the meantime how do I determine the CYA level?

    What is the "shock" level? Is this a chlorine #?

    Seems like these are the keys to getting my pool in order; that and filtering, brushing and vacuuming.

    Thanks again!
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  5. #5
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    Re: Saltwater pool, can't get rid of algae

    What is the "shock" level? Is this a chlorine #?
    Yes. Your pool has algae because you do not have enough chlorine in it. To kill the algae, you cannot simply put in some more chlorine....you must "shock" the pool by elevating your chlorine to a predetermined level and then HOLDING IT THERE by adding more chlorine constantly until your pool is crystal clear. ONLY THEN can you let the chlorine level come back down to a normal maintenance level.

    Unfortunately, that shock level depends on the level of your CYA and you can't test for that. I would wait for your kit to come in so you can test and, meanwhile accumulate lots and lots of Clorox....much more than you think. Once you get a kit that will test accurately, you can post test results here and everyone will help walk you through the shock process and your pool will be crystal clear......honest!!
    Dave S.
    Site Owner 42k vinyl and concrete pool, 1.5hp pump, 140gpm filter, No SWG
    TFTestkits owner
    TFTestkits , PoolMath , Pool School

  6. #6

    Re: Saltwater pool, can't get rid of algae

    I was thinking of going out and trying to find a test that would test for cya today so that I could get started. I am afraid that by the time the ordered test gets here my pool will be a swamp - we are supposed to have rain for the next 5 days!

    Is there anything I can do in the meantime to keep the algae somewhat at bay?

    Thanks so much for all of your input!
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  7. #7
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    Re: Saltwater pool, can't get rid of algae

    The tests ship quickly from TFtestkits.
    YOu can have the CYA level tested at most pool stores.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  8. #8

    Re: Saltwater pool, can't get rid of algae

    Ok, I found a test kit locally that shows my CYA. I just tested my water and here are the numbers for my 25,000 gallon, saltwater pool with DE filter:

    Total Chlorine - 0
    Free Chlorine - 0
    PH - 8.4
    Alk - 100
    CYA - 40
    Hard - 300

    My pool water is clear, but there is algae on the walls and floor of the pool. Again, I added chlorine bleach the past two days, and (2) 40 lb bags of salt.

    It has been very windy these past few days, we have a lot of pecan trees close by that are dropping the little green fuzzy things, pollen is everywhere and the temperature is probably going to hit 90 today - great combination right?
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  9. #9
    Mod Squad JohnT's Avatar
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    Re: Saltwater pool, can't get rid of algae

    Quote Originally Posted by agarza8543
    Total Chlorine - 0
    Free Chlorine - 0
    That's your problem. Add chlorine, and keep adding it whenever it drops. Here's a good discussion of the shocking process Shocking Your Pool

    Once you get the algae cleaned up, you need to raise your CYA to a level appropriate for your SWCG.
    TFP Moderator
    20K Gallon 20X36 Vinyl Inground
    Hayward S244T Sand Filter with 1HP Whisperflo Pump. Liquidator C-201 and Solar Heat

  10. #10

    Re: Saltwater pool, can't get rid of algae

    Thanks to everyone who answered my questions - I truly appreciate it!
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  11. #11
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    Re: Saltwater pool, can't get rid of algae

    Quote Originally Posted by agarza8543
    Ok, here are the numbers for my 25,000 gallon, saltwater pool with DE filter:
    Total Chlorine - 0
    Free Chlorine - 0
    PH - 8.4
    CYA - 40

    My pool water is clear, but there is algae on the walls and floor of the pool. Again, I added chlorine bleach the past two days, and (2) 40 lb bags of salt.
    It has been very windy these past few days, we have a lot of pecan trees close by that are dropping the little green fuzzy things, pollen is everywhere and the temperature is probably going to hit 90 today - great combination right?
    You have algae in the water; it may look clear because the SWG is running but if there is algae in any part of the pool it's in the water. The ONLY way to kill it is by shocking the pool, with bleach. Using the "super-chlorinate" feature of the SWG will not add chlorine fast enough AND it will shorten the life of the SWG cell.

    Before you start shocking you need to drop the PH to 7.2 or 7.4.
    Pools with SWG's have a normal PH rise but chlorine is more effective at a lower PH so decrease the PH then shock.

    The pecan trees aren't helping right now, but you have to get enough chloring into the water to kill the organics, from the trees and the algae.
    ... and brush while you are at shock level and afterward !
    Terry in NC
    Triad Region of NC
    18x37 Vinyl IG (24,000 gal.), BBB & GoldLine AquaLogic PS4 SWG, Hayward 1 HP Superpump / Hayward Sand Filter / Polaris 280 cleaner / 6 deck jets / Sheer Descent Waterfall (in coping) / Brick Red Concrete Coping / Stamped Concrete Deck
    Lots of oak trees, maple trees, *and* leaves!

  12. #12

    Re: Saltwater pool, can't get rid of algae

    Ok, so I need to shock the pool with bleach, lots of it, until I reach the recommended level shown on the pool school shock chart - got that. The level of shock for my pool shows that the CYA level should be 60? My CYA is currently at 40, so does that mean I need to raise it?

    I also need to lower the PH.

    How long do I keep the chlorine at shock level? Until the algae goes away and stays away for a few days?

    I must say that the salt water pool was sold as a "care free" pool, I am not feeling it right now. I appreciate everyone's responses.

    25,000 gallon saltwater pool with raised spa, Hayward 6020 de filter, aqualogic PS-8 controls, 2 hp pump.
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  13. #13
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    Re: Saltwater pool, can't get rid of algae

    No - use the non-swg section for your shock level.
    Once you have the algae issue resolved, yes, you should raise the CYA. But complete the shock process first.

    Read:
    Shocking Your Pool

    Use liquid chlorine or bleach for shocking.
    Helpful links: Pool School; CYA/Chlorine Chart
    24' round AG pool, 52" high, Raypak heater; Waterway 2 spd Pump;
    150 Sq ft. Clearwater Cartridge Filter; Former and DISSATISFIED "Pool Frog" owner
    http://www.PerfectlyClearPoolService.com

  14. #14
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    Re: Saltwater pool, can't get rid of algae

    Quote Originally Posted by agarza8543
    Ok, so I need to shock the pool with bleach, lots of it, until I reach the recommended level shown on the pool school shock chart - got that. The level of shock for my pool shows that the CYA level should be 60? My CYA is currently at 40, so does that mean I need to raise it?
    I also need to lower the PH.

    How long do I keep the chlorine at shock level? Until the algae goes away and stays away for a few days?

    I must say that the salt water pool was sold as a "care free" pool, I am not feeling it right now. I appreciate everyone's responses.

    25,000 gallon saltwater pool with raised spa, Hayward 6020 de filter, aqualogic PS-8 controls, 2 hp pump.
    Don't raise the CYA level until the algae is gone... Raising it will make the shock level higher.
    You keep the pool at shock level until...
    a) You loose less than 1ppm of chlorine overnight
    b) your CC level drops and stays below 0.5 AND
    c) your water / pool is clean!

    SWG's make things easier, but they have to run enough to generate the chlorine.
    Terry in NC
    Triad Region of NC
    18x37 Vinyl IG (24,000 gal.), BBB & GoldLine AquaLogic PS4 SWG, Hayward 1 HP Superpump / Hayward Sand Filter / Polaris 280 cleaner / 6 deck jets / Sheer Descent Waterfall (in coping) / Brick Red Concrete Coping / Stamped Concrete Deck
    Lots of oak trees, maple trees, *and* leaves!

  15. #15
    Mod Squad Butterfly's Avatar
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    Re: Saltwater pool, can't get rid of algae

    Don't raise your CYA until you are done shocking.
    This will make your shock level lower (taking less bleach/liquid chlorine to reach) and cost less!
    Plus, you will haul fewer jugs

    You are done shocking when you meet the three criteria (copied from Pool School):
    CC is 0.5 or lower;
    An overnight FC loss test shows a loss of 1.0 ppm or less;
    And, if you don't have a FAS-DPD test kit, the water is clear.
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  16. #16

    Re: Saltwater pool, can't get rid of algae

    Again, thanks to all of you for your help, this is quite overwhelming trying to get everything right.

    Ok, I understand that I need to shock until I get the results listed.....but what is CC? I don't see it in the pool school pool chemistry list.
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  17. #17
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    Re: Saltwater pool, can't get rid of algae

    Quote Originally Posted by agarza8543
    ...but what is CC? I don't see it in the pool school pool chemistry list.
    A simple definition: CC is the bad or used up chlorine (combined chloramines?). FC is the chlorine available to fight the bad stuff.

    When the CC is 0.0 or even 0.5 you don't "smell" chlorine in the pool. It's the higher CC level that makes poorly sanitized chlorine pools "smell".
    -Terry
    Triad Region of NC
    18x37 Vinyl IG (24,000 gal.), BBB & GoldLine AquaLogic PS4 SWG, Hayward 1 HP Superpump / Hayward Sand Filter / Polaris 280 cleaner / 6 deck jets / Sheer Descent Waterfall (in coping) / Brick Red Concrete Coping / Stamped Concrete Deck
    Lots of oak trees, maple trees, *and* leaves!

  18. #18
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    Re: Saltwater pool, can't get rid of algae

    It is a lot of info to digest. Let's just take one thing at the time and we will keep it simple.

    Really, right now all you need to do are two things:

    1. If you have not already done so, lower the pH to around 7.2 - 7.4, and

    2. Maintain shocking your pool.

    After you are done shocking, we'll help you get it balanced. No worries
    TFP Moderator TF100 Test Kit TF100 TestKit YouTube Channel PoolMath
    You're done SLAMing when:
    1)You lose 1ppm or less FC overnight, & 2)You have .5ppm CC's or less, & 3)your water is clear.

    ~ One should not use a sledge hammer to swat a mosquito. ~

    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

  19. #19

    Re: Saltwater pool, can't get rid of algae

    I have added PH minus to my pool in an attempt to lower the ph to an acceptable level, before I add the bleach this evening.

    I am going out to scrub the pool walls and try to get to the bottom - it's twelve feet and I'm not sure I can reach, but I can get close.

    I don't understand how to measure for the CC, but I guess I will cross that bridge in a few days when the balance is better.
    25,000 gallon saltwater pool with raised spa, Hayward de filter 6020, 2 hp pump, aqualogic PS-8 Controls - Dallas, TX

  20. #20
    Administrator JasonLion's Avatar
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    Re: Saltwater pool, can't get rid of algae

    If I read correctly, your current test kit measures FC (free chlorine) and TC (total chlorine). You can calculate CC easily from those two: CC = TC - FC.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
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