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Thread: TDS of 3700 after changing water

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    TDS of 3700 after changing water

    I just changed my pool water 2 weeks ago because the CA had reached 1000ppm. I just took a sample of the water into Leslies for testing and they reported that the CA was 200ppm but the TDS reading was 3700 whereas it should have been closer to 350! The only chemicals I added after the complete change was 2.5# CYA, along with 2 gall
    of liquid Chlor and 1 gall muriatic acid. and apart from the cya the acid and CL were added in stages over that 2 week period. The suggested remedy for this was to change the water again (to what point if I use the same water supply co) or to add some chemical for around $50. Don't remember what.

    Could this be for real?

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    Re: TDS of 3700 after changing water

    Welcome to TFP!

    Well, the most important piece of advice we can give here is ignore almost everything Leslies ever tells you about water. In this case specifically, TDS is an old and fairly meaningless measure of water quality. It is not the total that matters, it is what specifically is dissolved that matters. Most of that 3700 (if that is a real number) is probably just salts, which are relatively harmless.

    So the first thing I am going to tell you is that you might not have to replace any water and almost certainly don't have to replace all of it. If you would like us to help you get better at managing your own pool then there are a few things you will need to do to get started:

    Step 1: You need accurate test results. For various reasons we really can't trust any pool store testing as they are rarely a reliable source of accurate testing. You need your own kit, but not just any one. We strongly recommend the TF-100 or K-2006 as they have all the necessary tests, including the FAS-DPD chlorine test that is missing from almost all other kits. I have a link in my signature to one store that carries them, and no I do not get a kickback if you buy there.

    Step 2: We need some information on your pool. Please update your signature with the information outlined here: What we need to know to answer your questions

    Step 3: While waiting for your kit to arrive you should start reading up to get an idea how we operate and what you will need to do to care for your pool going forward so you can avoid getting questionable pool store advice in the future. Here are a couple links that will give you a good foundation on which you can build your pool knowledge:
    Pool School - ABCs of Pool Water Chemistry
    Pool School - Recommended Pool Chemicals
    Pool School - Recommended Levels


    I hope you find this helpful and please ask any questions, we are here to help!
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

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    Richard320's Avatar
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    Re: TDS of 3700 after changing water

    Welcome!

    TDS is useless. I don't know what mine is or has ever been, but I've never had green water and the scaling I inherited is slowly disappearing.

    So take a sample of the tap water you used to fill the pool to Leslies and ask what the TDS is in that. Odds are, it will also be super high. Then you ask how replacing the water with that will change things for the better. Then you leave and only go back when you need obscure bits of hardware or pool toys that are on sale.

    If you don't have your own test kit, you'll be at the mercy of the pool store forever.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
    Troublefree does not mean Maintenancefree. It's like brushing your teeth: You can spend a couple minutes a day and pennies a week or go to the dentist once a year and spend several thousand dollars.
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    Mod Squad tim5055's Avatar
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    Re: TDS of 3700 after changing water

    Quote Originally Posted by pflood4150 View Post
    ....to add some chemical for around $50.
    Could this be for real?
    Yes, it is the way they make extra profit. As others have said, take control of your pool. Get your own test kit and don't bother taking them any more samples of water.

    Welcome to TFP!!
    TFP Moderator 39 X 18 23,000(ish) freeform gunite; built 2007ish; Pentair Triton II TR100 600lb Sand filter; 2 HP Pentair pump with 2.2 HP AO Smith single speed motor; 2 skimmers, 1 main drain, 4 returns w/waterfall, Stenner 45MHP2 3GPD running@ 60% - 15 gal Tank; heated by the sun CYA 200+ when I started - 50 now. Dolphin Supreme M5 Pool Cleaner. Hot Springs SX Spa, 285 gallon

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    Isaac-1's Avatar
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    Re: TDS of 3700 after changing water

    What they all said, using TDS to manage water is straight out of the 1960's (ok maybe the 1970's), back when there were not easily available tests for each of the primary things (salts, CYA, Calcium) that make up TDS
    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
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    Re: TDS of 3700 after changing water

    I would suspect that that number is unlikely. Have it retested somewhere else. You could use the k-1766 to measure chloride specifically.

    If you can get a new test of the tds, the calcium hardness and the salinity based on a chloride titration test, that would help better understand what you're dealing with.

    What was the source of the water? If you bought the water, the seller should be able to provide a water quality report.

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    Re: TDS of 3700 after changing water

    I do use a Taylor test kit K-2006 but this does not test for dissolved solids. The test meters for TDS are very expensive, and so far as I know they do not test for specific dissolved solids. It seems that unless I know what they are, how can an unknown be treated? Like you, I do not trust Leslies, the only reason I took a sample of my new water to them was for a CH test as I had ordered a replacement reagent for my kit which had not arrived. I had stopped using the store nearest to me after I was lied to by the manager who claimed that the unscented 8.2% bleach I was using was totally different to Chlorine and not just a lower strength! Seems all their employees are just as bad! They also claimed the phosphates were high and I should buy their phos free - only $50.

    BTW Could not find link to edit profile,
    Gold Canyon Arizona,12000 gall pebbletek pool built 2009, Sand filter.

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    Re: TDS of 3700 after changing water

    Tds just gives the total. A chloride titration test can help determine if most of the tds is from salt.

    Where did you get the water?

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    Re: TDS of 3700 after changing water

    TDS is not important. You do not need to test for it, you do not need to do anything about it. You do need to get your reagents for the calcium test, since that in range is very important with your pebbletek pool, but there is no reason to worry one bit about TDS.
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
    Pool School - PoolMath - HIGHLY Recommended Test Kits

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    Re: TDS of 3700 after changing water

    TDS test meters are not very expensive I have one that I bought for under $50 last year (for hydroponic gardening, not pool stuff), and I think Amazon has models starting under $15
    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~

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    Re: TDS of 3700 after changing water

    When one is expecting a tds of 350 on a fresh fill and it comes in at 3700, it might indicate that there might be a quality issue as the water is not what was expected.

    TDS affects ths CSI, which is relevant to the plaster.

    The salt level will affect a SWG.

    If the source water is at 3700 ppm, then it's only going to get higher with evaporation and refill. If there's a SWG, the salt level could quickly get too high for the unit to operate.

    In any case, it wouldn't hurt to better understand the source water to manage the pool water quality going forward.

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    Re: TDS of 3700 after changing water

    Quote Originally Posted by pflood4150 View Post
    BTW Could not find link to edit profile
    Click SETTINGS upper right and then profile and signature are lower left.
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