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Thread: New spa low, constant low fc readings?

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    Join Date
    Jul 2008
    Location
    Placerville, CA
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    44

    New spa low, constant low fc readings?

    I'm a new spa owner, purchased a Sundance spa that was on display at a home show and the spa has 'clearray' purification system.
    We've had the spa approx. 4 weeks and I am constantly finding 0 fc readings. I have had a salt water pool in the past, so I am somewhat familiar with the chemical process. I have been reading in the forum and pool school about how different spa chemistry is and I'm a little confused. The owner of the store I bought our spa from briefly went over the chemistry, and gave me a small supply of chemicals that they recommended.
    I here are my current test numbers as of this morning: Note that I added 'spa chlorine' 2 days ago and brought the FC level up to 10. So in just 2-3 days with no use of the spa it dropped to 0 fc.

    FC 0
    PH 7.8
    TA 80
    CH 280
    CYA 35
    Temp 101

    The owner also recommended throwing in a couple teaspoons of 'spa oxidizing shock' after every use which we have been doing.

    I have been reading about changing to liquid chlorine or bleach, but I am not sure what I should do or where to start?

    Thak you for your time!
    340 gallon Sundance Spa

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    Join Date
    Oct 2017
    Location
    Roscoe, IL
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    221

    Re: New spa low, constant low fc readings?

    Start here: How do I use Chlorine in my Spa (or pool)?)

    With your CYA at 35 you'll want to stop using dichlor as you have been using and switch to bleach now. Check your FC daily and add as needed. With my last fill in mid January it took just over a week to add enough dichlor to get the CYA to 30, so if it's taken you a month to get to 35 you're really not adding enough chlorine.

    Dropping from 10 ppm to zero in two days does seem a little fast. My guess is that because you've let it drop repeatedly to zero waste isn't getting oxidized completely and is building up or something is growing. Just get the FC up to shock range, then allow to drop to the proper range and keep it there by daily checks and chlorine additions. Once you track it for a few weeks to a month you might get the hang of it and can start checking every other day or so. Proper FC ranges are in the chart below. For a CYA of 35 shock is 14 ppm and target range is around 6 ppm.

    Pool School - Chlorine / CYA Chart
    Hot tub: Indoor Intex 28409E "Six Person" inflatable. 290 gallons. Taylor K-2006 test kit with Taylor 9265 Speedstir and TFT CYA test. Using dichlor/bleach/borax/muriatic acid.

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    Re: New spa low, constant low fc readings?

    Thank you for the information and links! I will get some bleach tomorrow and hopefully get a handle on it. Thanks again for your time and information!
    340 gallon Sundance Spa

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    Alwayswantedapool's Avatar
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    Jun 2015
    Location
    York SC
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    Re: New spa low, constant low fc readings?

    Also, for me to maintain chlorine levels, I always add 1 oz per person per hour after a soak. So if the wife and I are in the tub for 45 minutes then when we get out I add 2 oz. That helps a lot to keep the fc up.

    Mark, Pool: 30,000 gallon, IG Vinyl, Pentair Superflo Variable Speed 1.5 HP pump, Hayward S220T Sand Filter, Taylor k-2006 Test kit with speedstir. Dolphin Nautilus Plus.
    Hot Tub: Hot Spring Grandee 450 Gallons, Ace System (Salt water Chlorine Generator) Dichlor / Bleach method. Taylor K1766 Salt Test.

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    Re: New spa low, constant low fc readings?

    Quote Originally Posted by Alwayswantedapool View Post
    Also, for me to maintain chlorine levels, I always add 1 oz per person per hour after a soak. So if the wife and I are in the tub for 45 minutes then when we get out I add 2 oz. That helps a lot to keep the fc up.
    Great input! Thank you very much for the tip!
    340 gallon Sundance Spa

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    Oly's Avatar
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    Jun 2017
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    Fresno, CA
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    Re: New spa low, constant low fc readings?

    Once your water is balanced and you have moved to liquid bleach, be sure to test your CYA levels at minimum once every three weeks until you learn your system, as the CYA will move lower much faster than a pool. Easy to switch to back to dichlor until your CYA is 30-40 ppm. We also use 1oz of 10% bleach for each bather added after we are done. Another important test is the CC, combined chlorine as it will rise over time if the spa is covered after use. Uncovering the spa will help slowly lower the CC but when it gets too high you are nearing the clean, drain, flush and refill stage of spa maintenance in my opinion. Our spa is 250 gallons and during peak use we clean and refill after 75 days now.
    27,000 gallons of central CA well water housed in a fiberglass coated concrete/plaster pool, dug into the most productive top soil on earth and surrounded by an urban forest.
    Cleaned with a Pentair 48 sq ft DE filter and a Dolphin Discovery (S200) robot. 250 gal Hot Springs Solana RX stand alone spa. Taylor K-2006. My first thread... New Old House, New Old Pool....

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    Placerville, CA
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    Re: New spa low, constant low fc readings?

    Thank you for your input! I will definitely keep an eye on the CYA level for sure!
    340 gallon Sundance Spa

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