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Thread: Low chlorine levels

  1. Back To Top    #1

    Low chlorine levels

    I am a new pool owner and I am having trouble keeping my chlorine levels up. Our pool is approx 25,000 gallons and is in the direct sun, with no shade all day.

    We got our house about a month ago and prior to that the house was empty, it was a foreclosure, I'm not really sure if the pool was being taken care of while it was empty...

    After reading on this site how to care for a pool I decided that I would test and adjust my chemicals on a weekly basis. The first time I tested the FC level was 0. I wasn't too worried about it because I wasn't sure when the last time chlorine had been added. I added 160oz of 6% bleach, the following week I tested the chemicals and again the FC level was 0, I again added 160oz of bleach.

    So, I thought that I just needed to add chlorine more often, so I decided that I would test every day for the next week to see when the level dropped that way I would know how often I would need to add more. The next morning I was shocked to find that the level was again at 0! So I added another 160oz, the next morning FC was still 0. So then I doubled the amount and put in 320oz, the next morning the FC was at 4, this only lasted one day, the FC was at 0 the next morning.

    I have tried using different test kits thinking that I was testing something wrong, I had the water tested at Leslies and they came up with the same results. I thought maybe the pool was bigger than estimated, but whenever I add muratic acid to adjust the pH it adjusts as it should for the amount added. The CC level has always been 0, so to my knowledge there is no bacteria in the pool.

    The pool looks great, crystal clear. The water is not irritating to the skin. The CYA level is 60, which seems to be a little on the high side but the pool is in the direct sun all day. I have read a little about chlorine lock but the there are a lot of mixed reviews and I am not sure what to believe.

    The pool store told me to drain 1/3 of the pool and tried to sell me a bunch of expensive chemicals. Any suggestions on what to do?

    Here what my chemicals are at today
    Calcium hardness=480
    25,000 gallon IG pool, waterfall spill over from spa. Cartridge filter. 1.5hp hayward pump. From Modesto, Ca. Summers are dry and hot, temp is usually in the 90s+, often reaching 100+ degrees. Winters are cold with temps ranging from 30-60 degrees. Pool is in the full sun with no shade all day.

  2. Back To Top    #2

    Re: Low chlorine levels

    There is some sort of organics in the pool that is consuming chlorine. Or it has ammonia.

    What sort of test kits do you have available? We find test strips to be worse than useless pretty often. Other test kits can be good, if reagents are not expired.

    What is your location?

    What does the pool water look like? Clear & sparkling or dull or cloudy? Blue or greenish blue or green? Any algae on the walls, sides, nooks and crannies?
    23,000 gallon in ground pool with rock waterfall and spillover spa, Aqualink control system, Polaris 380 cleaner, Purex Triton Clean&Clear Plus cartridge filter. Located in The Woodlands, Texas.

    Pool owner since Nov 2008, Trouble Free since April 2009. Happy to help when I can.

  3. Back To Top    #3

    Join Date
    Aug 2010
    Boston, MA

    Re: Low chlorine levels

    Welcome to TFP!

    Testing and adding chlorine must be done every day. Some people can get by with every other day once they're well familiar with their pool's behavior, but certainly not starting out.

    Additionally, 160 oz of 6% in 25000 gallons is only about 3 ppm. With CYA at 60, you need to keep the FC above 5 ppm at all times, and consumption rates of ~2ppm per day are pretty typical. So there has been effectively no sanitation of this pool for an extended period of time.

    Therefore, you will need to shock the pool following the instructions in Pool School. Afterwards keep on top of that FC level. Rereading Pool School's chemistry sections would also be advisable.
    20k gallon IGP
    Plaster over gunite
    3/4 hp Hayward pump
    Purex Triton DE filter
    TF100 test kit w/ speedstir

  4. Back To Top    #4

    Join Date
    Apr 2011
    Lynchburg VA

    Re: Low chlorine levels

    My pool is slightly larger then your but on average I use a full 1.4G jug of chlorine every day during the summer months and my CYA is around 55. I check the levels on my pool every day for the most part.
    18x36 Vinyl In-ground w/roman ends 27,400G, Hayward 3/4hp with 300# sand filter. Hayward heat pump heater

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