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Thread: Differences in chem test results

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    pinguy's Avatar
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    Differences in chem test results

    I just got a new inground pool and have a question about testing.

    I have 2 liquid drop test kits, the "instant" test strips, and took a water sample into a pool store. I'm getting very different numbers from each test and I don't know what to trust.

    For Alkalinity the pool store says my sample was 100ppm. The test strips show a similar range, but my drop test kits show me 160/180ppm.

    For Calcium hardness, the pool store/test strips say 110, but the drop tests show closer to 200.

    For PH, pool store says 7.8 but the all my home tests say 8.5-9.5.

    What tests should I trust?

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    Mod Squad tim5055's Avatar
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    Re: Differences in chem test results

    Neither of them.

    Not much credence is given to pool store testing around here and test strips are even worse. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing

    You need to do your own testing with one of the recommended test kits. You can buy a kit at a pool store, but again the pool store kits generally won't cut it. To effectively practice the TFPC methods, the FAS/DPD chlorine test is essential. All these kits contain that test while very few other kits do.
    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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    Mod Squad jblizzle's Avatar
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    Re: Differences in chem test results

    Which drop based test kits do you have? Those are the only type that we trust.

    Please add your pool details to your signature as described HERE as it will help us help you.
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    Re: Differences in chem test results

    Thanks, it's a 28k gallon gunnite/Diamond Brite finish. All pentair mechanics I believe.

    We just got water in it Friday. I was told to wait until Monday to add any chlorine, and then another 3 weeks to add the salt.

    I have a Leslie/Taylor drop kit as reccomended.

    The only thing that makes me nervous right now is adding calcium. Pool guy told me if that gets messed up the whole thing needs to be drained.

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    Re: Differences in chem test results

    What does the drops test that YOU have say?
    Dave S.
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    Re: Differences in chem test results

    I just did another round of tests.

    TA: 160 ppm
    PH: 8.2
    CH: 160 ppm

    I added 3lbs dry acid today. I was going to add 3 more each day until the TA/PH was on point. After that I was told to add 20lbs calcium daily until it reaches 200-400.

    By monday I was going to fill my chlorinator with tabs and shock the pool/add chlorine stabilizer.

    Please advise, thank you!

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    Mod Squad jblizzle's Avatar
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    Re: Differences in chem test results

    What Leslie's test kit model number?
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    Re: Differences in chem test results

    Quote Originally Posted by jblizzle View Post
    What Leslie's test kit model number?
    18-576 is the only number I can find

    It looks like this:
    Attached Images Attached Images

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    Mod Squad jblizzle's Avatar
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    Re: Differences in chem test results

    That is the equivalent of the K-2005 which is not one of the Recommended Test Kits because it does not have the FAS-DPD chlorine test. You can add the FAS-DPD Chlorine Test to give you the equivalent of the recommended K-2006 ... order some CYA refill while you are at it.

    EDIT: actually the comparator in your kit is different from the K-2005/K-2006, but the pH is the same as that used in the TF-100 (although the TF-100 has the OTO test and not the DPD which I think yours does) ... if that is not confusing ...

    - - - Updated - - -

    I do not even see that test kit on their website ... hope it is not really old.
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    Differences in chem test results

    I think this got lost in all the posts but I just wanted to say that if you have a new pool with a new plaster surface and new water then you need to be really careful about lowering your TA and pH. I'm mobile right now so I can't easily find the link for plaster startup but you need to be careful

    New plaster needs time to cure and having the right pH and TA is critical for proper plaster care.

    Can anyone post the plaster start up link??


    Matt
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    Re: Differences in chem test results

    Quote Originally Posted by jblizzle View Post
    That is the equivalent of the K-2005 which is not one of the Recommended Test Kits because it does not have the FAS-DPD chlorine test. You can add the FAS-DPD Chlorine Test to give you the equivalent of the recommended K-2006 ... order some CYA refill while you are at it.

    EDIT: actually the comparator in your kit is different from the K-2005/K-2006, but the pH is the same as that used in the TF-100 (although the TF-100 has the OTO test and not the DPD which I think yours does) ... if that is not confusing ...

    - - - Updated - - -

    I do not even see that test kit on their website ... hope it is not really old.
    All very confusing, but I'm learning. The box says free chlorine and DPD. Also expiration dates say Dec 2016 so I don't think it's too old.

    I can buy more stuff if I need to.

    So does the regiment that the pool guy suggested sound good?

    - 3lbs dry acid or liquid equivilent until TA is ideal
    - Same as above until PH is ideal
    - AFTER PH/TA is good, 20lbs calcium daily until 200-400ppm
    - This monday, add chlorine tabs/stabilizer/shock

    Also, can I add calcium and chlorine/shock and acid all on the same day? How far apart does that need to happen?


    Attached Images Attached Images

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    Re: Differences in chem test results

    Quote Originally Posted by JoyfulNoise View Post
    I think this got lost in all the posts but I just wanted to say that if you have a new pool with a new plaster surface and new water then you need to be really careful about lowering your TA and pH. I'm mobile right now so I can't easily find the link for plaster startup but you need to be careful

    New plaster needs time to cure and having the right pH and TA is critical for proper plaster care.

    Can anyone post the plaster start up link??
    The builder/pool guy both seemed VERY anal about protecting the gem coating, but neither had an issue with 3lbs of acid daily until the levels stabilize.

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    Re: Differences in chem test results

    Quote Originally Posted by pinguy View Post
    The builder/pool guy both seemed VERY anal about protecting the gem coating, but neither had an issue with 3lbs of acid daily until the levels stabilize.
    My thought process here is that freshly applied plaster takes time to cure. It cures by sucking CO2 out of your water. The only source of CO2 in your water is your carbonate alkalinity. Therefore you don't want to drop it too quickly.

    You can search TFP for plaster curing and read lots of interesting threads about it.

    At the end of the day I suppose you have to do what your builder says to maintain warranty so just be cautious when adding chemicals and keep an eye on your levels.


    Matt
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    Re: Differences in chem test results

    Quote Originally Posted by pinguy View Post

    By monday I was going to fill my chlorinator with tabs and shock the pool/add chlorine stabilizer.

    Please advise, thank you!
    i hope you are not planning on using tabs long term as your cya will eventually become too high
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    Re: Differences in chem test results

    Quote Originally Posted by aussieta View Post
    i hope you are not planning on using tabs long term as your cya will eventually become too high
    No, only the first month. Then we'll switch to the SWG.

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    Mod Squad pooldv's Avatar
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    Re: Differences in chem test results

    While you are following the builder's recommendation you can use Pool School - PoolMath to check the effects of what you are adding and see how that compares to Pool School - Recommended Levels.
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    pinguy's Avatar
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    Chemistry & New Plaster (pictures)

    I'm brand new to pool care but I've been reading and learning so much from this place the past couple days. I'm starting to become obsessive over pool chemistry

    The pool was just finished with the plaster and water being added on Thursday (4 days ago). It's a 25000-28000 gallon gunnite pool. I have the a Taylor test kit that has everything but the powder FAS/DPD, which I'm going to order.





    Here is the pump system. It's all Pentair stuff for the most part. The builder said to bypass the SWG for the first month so the plaster can set and use the Trichlor system with tablets.







    Everything LOOKS great, but my TA and PH are through the roof at 160PPM and 8.5+. The ONLY thing I've added to the water so far is 12lbs dry acid, and neither number moved a bit. Pool math told me 7lbs dry acid to get from 8.5 to 7.2, so I'm assuming the PH is over 8.5 since that's only how far the Taylor test goes.

    So, how much Acid can I put in at a time? A couple posts here made me nervous about adding too much and damaging the plaster. The pool guy told me 3lbs a day of dry or MA liquid equivalent. But he also recommended test strips

    Tomorrow I'm going to fire up the tri-chlor with tabs, and add some solid chrlorine shock/stabilizer tomorrow per the builder's orders. Will that help out with lowering the PH?

    I know you all don't like trichlor systems or shock powder but it's only temporary, and I kind of need to stick to what the builder says for this first year.

    I'm looking at getting this guy ready to swim in by next weekend. THANKS FOR ALL THE GREAT INFO HERE

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    Re: Differences in chem test results

    Looks like my theads got merged. Sorry for making a new one, the last one was buried and I had some new questions.

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    Re: Differences in chem test results

    Quote Originally Posted by pooldv View Post
    While you are following the builder's recommendation you can use Pool School - PoolMath to check the effects of what you are adding and see how that compares to Pool School - Recommended Levels.
    Yes! The pool school numbers aren't far off from what the builder gave me.

    I've been playing around with pool math. It said to add 7lbs dry to lower the PH from 8.5 to 7.2. I added ~9lbs and no change

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    Mod Squad jblizzle's Avatar
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    Re: Differences in chem test results

    It is much better to use muriatic acid.

    Did you have your TA set in PoolMath as that impacts the pH calculation.

    Also I see a dreaded Nature 2 in your pictures. We do NOT recommend adding minerals/metals to your pool as you could stain your new plaster and turn your hair green. I highly recommend you remove the minerals from the canister.
    Jason, TFP Moderator
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