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Thread: Total Dissolved Solids question

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    Join Date
    Aug 2015

    Total Dissolved Solids question

    I have a question pertaining to total dissolved solids(TDS). The chemical companies literature says once it's >1500 it's time for a water change and the spa mfg and spa shop say when it's >2500 it's time for a change. I've spent hours upon hours reading this forum and see very little mentioned about it at all, plus my Taylor test kit doesn't mention it either. So I'm wondering how important is it really, if at all? I plan on changing my water every 3-4 months no matter what. So, is this something I even need to think about? Let me know your opinions.
    Caldera Vanto 375 gal
    Taylor k-2106 kit

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    Mod Squad JVTrain's Avatar
    Join Date
    Feb 2014
    Central Minnesota

    Re: Total Dissolved Solids question

    It's an irrelevant number. A well-maintained spa can be use for at least 3 months before a water change. Don't worry one bit about TDS. TDS is a number that is the sum of many other chemicals in the pool such as CYA, CH, salt, etc. Therefore, it's not very meaningful. Knowing the concentration of the individual chemical species is important.

    Stick to your 3-4 month plan as long as you always keep some FC in the tub and see the two stickies in this forum for our recommendations on chlorine or bromine spas.
    Joel - TFP Moderator - Minnesota - **Become a TFP Supporter!** Helpful Links: ABCs of Pool Water Chemistry - SLAM Procedure - Chlorine/CYA Chart
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    JoyfulNoise's Avatar
    Join Date
    May 2015
    Tucson, AZ

    Re: Total Dissolved Solids question

    Joel nailed the executive summary - don't worry about it.

    TDS was used in the past as proxy for how much "stuff" was on your water. Prior to cheap and reliable test methods for individual ions and chemicals, TDS was a way to quantify the quality of your water. The true way to measure was to take sample of water and evaporate/dry all the water from it and measure the weight of all the left over solids. Electronic methods eventually supplanted dry weight measures.

    Like so many things in the pool/spa industry, change and adoption of new standards is very slow. To this day, the effects of CYA on FC are still largely ignored even though the science has been established and proven for over 30+ years. Manufacturers are locked into regulations that haven't been updated in decades and are forced to quote "recommended levels" even though they make no sense or have little factual justification.

    Now, I command you, go and enjoy your spa !!

    Sent from my iPhone using Tapatalk
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Join Date
    Aug 2015
    Plano, TX

    Re: Total Dissolved Solids question

    Quote Originally Posted by JoyfulNoise View Post
    To this day, the effects of CYA on FC are still largely ignored even though the science has been established and proven for over 30+ years.
    I never knew about this until I found this site. I'm sure happy to be enlightened!
    Curtis- 20k gallon IG gunnite/plaster with hot tub/waterfall and "grotto"
    All Jandy equipment: 60sqft DE filter - 399k btu natural gas heater - Stealth pumps - iAquaLink RS8.
    Polaris 9400 on patrol.
    TF-100 in da house/TFP method in effect: FC=4-6, pH=7.5, TA=80, CH=250, CYA=50, Borate=50, CSI=-0.21

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    Mod Squad
    Join Date
    Aug 2012
    DFW, TX

    Re: Total Dissolved Solids question

    I don't know what the TDS is in my tub. I don't drain it very often either. Two times in 20 months or so, I think. I use this process to maintain my tub and it is awesome. We use it at least 3-4 times a week and almost every day most of the time.

    How do I use Chlorine in my Spa (or pool)?
    TFP Moderator
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