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Thread: Strange hardness test

  1. Back To Top    #1

    Join Date
    May 2007
    Location
    Rocklin, Ca
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    467

    Strange hardness test

    Now that we have been enjoying our pool for about a month, I have a testing question.

    As part of the original deal the PB is responsible for the chemical maintenance for the first 30 days which was up last Wednesday. I think they may be coming out for one more visit but I may tell them not to bother They have been doing less than a good job but that's another story.

    I bought an HTH 6 way test kit from Wal Mart until I get a TF Test Kit. Despite it's limitations it has been doing a pretty good job until today. Who knows, maybe it's still doing a good job and I can't tell what the tet is telling me which is the point of this post.

    I have been testing the water every couple of days to get some practive doing it as well as to keep tabs on what the PB is doing. So far the range of results have been:

    TC - (0-2) depending how recently they were here.
    pH - (7.4-8.0) and only 7.4 because I added some acid after I read that Pebble Fina is happiest at 7.4 during curing
    TA - (120-100) it has been trending down which I guess is good for when I start up the SWG
    CH - (250-280) it has kind of stabilized at 280. Out tap water is mostly snow run off and is not very hard at all.
    CYA - (0) I added 5 lbs of CYA about three days ago but have ran out of reagent. Pool calculator says I need to add about 8 lbs total.

    The problem started today when I tested the CH. After I put in the five drop of Hardness Indicator it didn't turn red like it normally does. This time it turned yellow. I know it wasn't but it looked a bit like muriatic acid. I didn't try the titration part of the test. Does any one know why the color went yellow instead of red?

    This mornings results were:

    TC - 4 I added about a gallon of bleach last night after a bunch of people were in the pool.
    pH - 7.2
    TA - 100
    CH - Who knows? Should've been around 280.
    CYA - Probably north of 30

    Thanks,

    Kevin
    11000 Gals, Intelliflo, Sta-Rite Cartridge, Polaris 360

    Pool I built in my old house: my-new-pool-build-t4534.html

  2. Back To Top    #2
    Guest

    Re: Strange hardness test

    I have seen this occur with inexpensive test kits. Your hardness test only has two reagents, correct? (indicator and titrant) I suspect is it linked to high chlorine levels but in this case the test seems to have problems with chlorine levels above about 4 ppm. The (discontinued) AquaChem 6 way kit had this problem also.

  3. Back To Top    #3

    Join Date
    May 2007
    Location
    Rocklin, Ca
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    467

    Re: Strange hardness test

    Waterbear,

    Thanks. That makes sense because the only other thing that is different from previous tests is the CL level. I will test it again today when the CL level will be a bit lower.
    11000 Gals, Intelliflo, Sta-Rite Cartridge, Polaris 360

    Pool I built in my old house: my-new-pool-build-t4534.html

  4. Back To Top    #4

    Join Date
    May 2007
    Location
    Rocklin, Ca
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    467

    Re: Strange hardness test

    Ok...now I'm stumped.

    Today I tested everything again and everything was pretty much as expected

    Cl - 2
    pH - 7.4 as expected since I ran the waterfall for many hours yesterday.
    TA - not much change here
    CH - test water was still yellow after adding the indicator

    I fully expected the indicator to behave normally since the Cl is now back down. How do others who run much higher Cl level test their CH?

    I still trust my indicator because I still get normal results when I test my spa which is a stand alone unit.
    11000 Gals, Intelliflo, Sta-Rite Cartridge, Polaris 360

    Pool I built in my old house: my-new-pool-build-t4534.html

  5. Back To Top    #5
    Guest

    Re: Strange hardness test

    The other thing that can cause interference is metals in the water. This is a problem with inexpensive test kits. Like I've said, I have seen this problem on inexpensive, 2 reagent test kits but not on the Taylor 3 reagent calcium hardness test.
    Have you tried testing your tap water with it?
    How many drops of indicator does the instructions tell you to add?
    My best suggestion would be to get yourself a GOOD test kit. The difference is night and day!

  6. Back To Top    #6

    Join Date
    May 2007
    Location
    Rocklin, Ca
    Posts
    467

    Re: Strange hardness test

    I just refilled my spa and the CH test on the fresh tap water was normal so I still trust that the reagent is ok. The kit I have is the HTH 6-Way and it it says to add 5 drops, mix and then titrate.

    I will be buying a TF Test Kit in the next day or two.
    11000 Gals, Intelliflo, Sta-Rite Cartridge, Polaris 360

    Pool I built in my old house: my-new-pool-build-t4534.html

  7. Back To Top    #7

    Re: Strange hardness test

    I'm curious as to whether the TF test kit solved the CH test problem for you. I'm experiencing the same problem as you did. With the HTH 6-way test kit, the sample turns yellow instead of red after CH indicator addition.

    ______________
    34000 gal 20x50 gunite/River Rok, 2HP Whisper Flo, Intellichlor IC40 SWG, MasterTemp 400, FNS Plus 60 DE, Easy Touch 8, Polaris CareTaker
    34000 gal 20x50 gunite/River Rok, 2HP Whisper Flo, Intellichlor IC40 SWG, MasterTemp 400, FNS Plus 60 DE, Easy Touch 8, Polaris CareTaker

  8. Back To Top    #8
    JasonLion's Avatar
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    Location
    Silver Spring, MD
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    37,887

    Re: Strange hardness test

    Seeing yellow instead of red on the CH test is fairly common with some of the cheaper test kits. As long as the color change remains clear, it doesn't usually affect the test results.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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