Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 8 of 8

Thread: CYA levels lowered by chlonine????

  1. Back To Top    #1

    CYA levels lowered by chlonine????

    I am working on getting my pool swim-able and 2 weeks ago when I got the water tested at a leslie's my CYA was at 60 and the chlonine level was low. Recently about a week ago I noticed some algae so I added 5lbs of pool-time shock plus to kill all the algae and hopefully have enough chlorine to last a week. About 5 days later i checked the chlorine and it was at 0 so i started wondering if the CYA was too high and causing the chlorine not to work properly. After reading many websites i am convinced not to use pool time shock plus because it will increase the CYA levels and the safest way would be to use liquid chlorine. So i added about a gallon of liquid chlorine last night and my chlorine level today is about 8ppm too high and CYA at 25 according to leslies.

    Everything i have read in the past points out that CYA cannot be lowered unless is drained partially/completely depending on the LEVELS. Now my concern is how come leslies test shows that my CYA is at 25 when two weeks ago was about 60. Is this possible?

    The pool looks great but I dont know how long the chlorine will last in the water. I always thought chlorine should last about a week. I will test the water daily to see how fast is being consumed. Its been about 90 degrees and the pool is in direct sun almost all day so I know that plays a part in the chlorine.

    I feel like I always have algae problems so I just starting using leslies pool perfect plus phos-free to hopefully lower the levels of phosphate in pool and control algae.

    I was told by leslies to add conditioner in my pool to bring the levels up but I am concerned this will actually cause a problem.

    What should I do????

  2. Back To Top    #2

    In the Industry


    Join Date
    Feb 2012
    Location
    Phoenix, AZ
    Posts
    728

    Re: CYA levels lowered by chlonine????

    Quote Originally Posted by oarmas25
    Everything i have read in the past points out that CYA cannot be lowered unless is drained partially/completely depending on the LEVELS. Now my concern is how come leslies test shows that my CYA is at 25 when two weeks ago was about 60. Is this possible?
    You are correct (that CYA will only be lowered by replacing water). And this goes to show how inaccurate pool store test results can be. It would be wise to get your own test kit and test your water on your own.

    Quote Originally Posted by oarmas25
    The pool looks great but I dont know how long the chlorine will last in the water. I always thought chlorine should last about a week. I will test the water daily to see how fast is being consumed. Its been about 90 degrees and the pool is in direct sun almost all day so I know that plays a part in the chlorine.
    Chlorine consumption is based on several factors..algae presence, CYA level, and sunlight.

    Quote Originally Posted by oarmas25
    I was told by leslies to add conditioner in my pool to bring the levels up but I am concerned this will actually cause a problem.
    Again, your intuition is correct. You should not add any more conditioner until you KNOW what your CYA is.

  3. Back To Top    #3
    Isaac-1's Avatar
    Join Date
    May 2010
    Location
    SW Louisiana
    Posts
    6,711

    Re: CYA levels lowered by chlonine????

    Edited to remove conflicting information and prevent confusion to newbie. Butterfly A much higher chance is one or both of the tests were wrong. This is part of why we so strongly suggest getting a good test kit like the Taylor K-2006 or the TFTestkits TF-100 (I use the TF-100), pool store testing is notoriously wrong. I just had some water tested for iron due to a rust/iron shavings contamination issue last week (I don't have an iron test since it is not normally an issue in my pool), and the pool store numbers were wrong more than right (they showed my CYA at 10, really at 25-30, CH at 80, really 160, and TA at 110 or so and really around 60-70).

    Ike
    Indoor 20x40 35,000 gallon vinyl pool with 1.5 HP 2 speed Jandy FloPro pump, Hayward EC75 Perflex DE filter, 11 4x12 Techno-Solis solar panels w/ Aquasolar controller, Aquabot Turbo T Robot Cleaner. Also LMI metering chlorine dispenser pump and HotSpring Jetsetter
    I use and endorse TFtestKits TF-100 from http://tftestkits.net
    ~Remember TFP counts on your donations to keep this site ad free~

  4. Back To Top    #4
    Mod Squad zea3's Avatar
    Join Date
    Jul 2009
    Location
    Houston, Texas
    Posts
    9,200

    Re: CYA levels lowered by chlonine????

    Hi, welcome to TFP! Pool store testing is notorious for being inaccurate, especially for CYA. The most common CYA test has a +/- 10ppm accuracy, meaning if you get a CYA result of 50 it could actually be 40 or 60. Part of the reason for the error is reading the test depends on noting the point when a black dot is no longer visible at the bottom of a test cylinder while pouring in the test solution. Lighting conditions and eye sight issues can effect how the test is read. Some stores will use a computer to run the CYA test, but the computer must be re-calibrated frequently to maintain accuracy. Plus the test is only as reliable as the individual conducting it. I would have another sample tested, preferably at another store and see if the result is anywhere near the previous one.

    This brings me to my next item. In order to take control of your pool you should have a high quality FAS-DPD test kit such as the TF 100. It will allow you to test very high levels of chlorine needed to complete the shock process and performing your own tests allows you to have more consistent results. You can test the pool every day or two and dose the pool as needed to keep it balanced.

    Now, chlorine will continually deplete as it oxidizes organic matter in the water. How quickly it depletes depends upon how much organic matter there is, and how much UV exposure the chlorine has. The CYA provides protection from the sun's UV rays. Too much CYA protects the chlorine so well it is rendered ineffective and allows algae to grow unchecked. CYA only "disappears" on its own when it is consumed by bacteria and that usually only happens over winter or when certain fertilizers are introduced into the pool. The whole "add shock once a week" thing is the expectation that a bag of shock will raise the pool to shock level (10ppm in theory) and it will take about a week for the chlorine to deplete to between 1-3 ppm. While that is standard pool industry recommendation, it does not take into account any variables such as bather load, or CYA levels.

    A properly chlorinated pool will not grow algae no matter how high the phosphate level gets. Chlorine will need to be replenished every day or two to keep it at recommended levels. Read through pool school and take a look at the pool calculator and you will learn more about caring for your pool.
    TFP Moderator
    Helpful links: TF Test Kits,TFP Pool School, PoolMath
    Vogue 21' round AG, Pentair 1 hp 2 speed pump, 36 sq ft DE filter, Hayward S180T 150# sand filter, Houston, Texas
    Love TFP? Become a
    TFP Supporter!

  5. Back To Top    #5

    Join Date
    Sep 2009
    Location
    Greentown, IN
    Posts
    914

    Re: CYA levels lowered by chlonine????

    Wow.. these people are fast! I was responding to your post and went to see if you had any responses yet and see several already.

    Welcome to the forum! This place is great and I'm thankful to have found it in time to start out on BBB. With their comments, and the pool school section, you will be well on your way to a much more beautiful and clear pool with little effort, and likely much less cost than you are used to. And, I concur... order a test kit... Pronto!!

    One thing I would like to add to their comments. You could add your pool specs to your signature line (go to user control panel, then profile, then edit signature) so that those trying to help you can have a better understanding of your pool size, make up- is it vinyl, plaster, etc.
    Indiana, ABG 24'x52" Galveston by Blue Cascade (Craigslist buy w/part of deck included), 13,500 gallons, Intex SWG, solar panels mix 2, TF-100 test kit.

    Test kits compared
    Purchase test kits

  6. Back To Top    #6

    Join Date
    May 2008
    Location
    NE Florida
    Posts
    51

    Re: CYA levels lowered by chlonine????

    Interesting timing on this post. I just went through something similar. I have a K2006 test kit and test at home. My CYA was 50-55 (repeated tests) before I started shocking the pool for a suspected mustard algae problem, that started after bringing my Cl levels down from 20 after shocking this spring. The algae started with a cl of 12 or so, despite holding chlorine overnight and having CC of less than 0.5. I think it was being harbored in some in floor cleaning runs that were stagnant which I have since corrected. So I ran the chlorine up to 25-30 for a week and it looks good again while the Cl level is dropping. I tested CYA again yesterday and now it is between 30-40. I repeated it today and it's still the same. So, I was wondering if the high Cl levels burned some of it off. There has been no rain or water added to the pool in that time frame.
    What ever caused the drop, I'm going to add more to get it back up to levels appropriate for my swg and hope the algae keeps at bay.
    22K gallon free form pebble tec pool, non screened, surrounded by 3, 100+ year old Live Oaks (pure misery for 3 months every spring) elevated non heated spa, jandy cl340 filter, Pentair Inteliflo 3hp pump, Jandy 1400 swg, infloor cleaning system which has had all outlets removed due to uselessness of system with the organic load the pool carries and now low rp

  7. Back To Top    #7

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,084

    Re: CYA levels lowered by chlonine????

    So, I was wondering if the high Cl levels burned some of it off.
    No. If it did, you would have to add CYA each time you shocked. However, I don't know why yours dropped.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  8. Back To Top    #8

    Join Date
    May 2008
    Location
    NE Florida
    Posts
    51

    Re: CYA levels lowered by chlonine????

    Just wondering since I had it quite high for a week trying to root out the mustard algae
    22K gallon free form pebble tec pool, non screened, surrounded by 3, 100+ year old Live Oaks (pure misery for 3 months every spring) elevated non heated spa, jandy cl340 filter, Pentair Inteliflo 3hp pump, Jandy 1400 swg, infloor cleaning system which has had all outlets removed due to uselessness of system with the organic load the pool carries and now low rp

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •