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Thread: Acuracy of Salt Test Strips

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    Acuracy of Salt Test Strips

    Hello all,

    I just finished adding 600lbs of salt to my pool in preparation for hooking up my SWG. I calculated I would need around 720lbs to get my pool up to the 3500ppm salt level needed for the SWG. I used an accutest strip to test the salt level after the salt had disolved into the water and got a result of 4.6 which equalls 1480ppm. give the amount of salt and my estimated pool volume of 25k gallons I was expecting a number about twice that. The salt I used was 10 bags of blue bag water softener salt from Home Depot and 5 white bags of pool salt from Home Depot. All bags were 40lbs for a total fo 600lbs. My readings as of Friday (7/22) evening are:

    FC: 4.5
    TC: 4.5
    PH: 7.8
    ALK: 100

    CYA has been hovering around 50 and I have not had to add much water so I expect it hasn't changed much. These numbers are a little off from the pool schooll ideal numbers so I was wondering if they can affect the test strip reading. Or can these test strips have inaccurate results?

    Roland
    I got nothing right now

  2. Back To Top    #2
    JasonLion's Avatar
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    Re: Acuracy of Salt Test Strips

    Give the pool 24 hours with the pump running for the salt to completely mix in before testing the salt level. It takes a while for the salt to mix uniformly throughout the pool.
    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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    Re: Acuracy of Salt Test Strips

    I didn't have a way to isolate my main drain so one problem is that the salt is heavier than the water and so the salinity of the bottom of the pool is higher and won't get pulled up by skimmers. Just hooked up my pool vac and left it on the bottom overnight which improved my readings significantly. You can test this by measuring the "instant salinity" when you put the pool vac in if you have your SWG hooked up already. Mine jumped about 1000 ppm.

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    Join Date
    Jun 2008
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    Texas
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    Re: Acuracy of Salt Test Strips

    First I would brush the pool to ensure the salt has dissolved and mixes.

    Second, the salt test strips are easy to mis-read. You want to read the tip of the white mark. I use a magnifying glass to ensure that I do not underestimate the height of the white line. My readings of the test strips have been within +- 200 of the salt level indicated by my SWG.
    30,000 gallon gunite in-ground with a spillover spa, Diving board and water slide
    Hayward 1 HP Super II filter pump, Hayward 24 " Sand Filter Pro Series using zeolite media
    Polaris 380 cleaner with ¾ HP booster pump, Hayward Heatmaster pool heater, AutoPilot DIG-220 Power Supply SC-60 cell
    Testing with the TF-100 Test Kit

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    Re: Acuracy of Salt Test Strips

    @JasonLion:

    Thanks for the quick response. I think I may have tested it too early as you suggested. I tested again this morning without having added any salt and it was up to around 5.8 (2400ppm). A 1000ppm improvement. I had some guests over yesterday who might have helped stir up the water a little too. I just got another 240lbs of salt which should be enough to get me where I need to be. Based on my calculations (4ppm per lb) I will need 300lbs to get me to 3600ppm.

    @Gaidal:

    Thanks for the suggestion to shut off the skimmer. I'll give it a try and see if that helps.

    RTS
    I got nothing right now

  6. Back To Top    #6

    Join Date
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    Re: Acuracy of Salt Test Strips

    I would only add 1/2 of what you think you need....wait a couple of days and add again....if you end up with too much you'll have to drain water to get it down
    Karl

    14,000g IG Plaster
    Intellicor IC40 SWCG
    DE filter-Nautilus FNS 60
    Polaris 280

  7. Back To Top    #7

    Re: Acuracy of Salt Test Strips

    So I finally got the salt generator up and running. After adding about 840lbs of salt total and waiting two days after the last bages were disolved I took a test reading. The strip read 4.8 which corresponds to about 1920ppm. I started up the Compupool CPSC24 and got it going. This unit tests for salt level and is giving a reading of 5100-5200ppm. So I 'm not sure which reading to believe. I'm inclined to believe the salt generateor because the water tastes real salty. I've heard that if salt levels are above optimal (3500ppm for this unit) that I should drain and refill to get the correct levels. What is the down side to leaving the level higher?
    I got nothing right now

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    franke's Avatar
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    May 2011
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    Re: Acuracy of Salt Test Strips

    My experiance with the Compupool has been that it reads very high, however adding 840 # to a pool that I expect to be less than 2000 gals. would raise the salt level pretty high. How old are your salt strips? At the moment I am using the Taylor drop test but when I was using salt strips they both read pretty close. I would get another batch of strips or the Taylor drop test and see which reading is closer.
    25000 gal Rectangle IG, Vinyl, SWCG -CircuPool SI45 Plus, Sand Filter, 3/4 hp Pentair pump with US motors echotech EZ variable speed motor

  9. Back To Top    #9

    Re: Acuracy of Salt Test Strips

    840 pounds of salt added to a 25,000 gallon pool will increase the salt level by 4,000 ppm. Most fill water already has some salt, so you're going to be above 4,000 ppm.

    You should take a sample of your pool water and your fill water to a pool store to have them tested with a salt meter.

  10. Back To Top    #10
    franke's Avatar
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    May 2011
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    Forest, VA
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    Re: Acuracy of Salt Test Strips

    I expect that you will be draining at least 20% of your water.
    25000 gal Rectangle IG, Vinyl, SWCG -CircuPool SI45 Plus, Sand Filter, 3/4 hp Pentair pump with US motors echotech EZ variable speed motor

  11. Back To Top    #11

    Re: Acuracy of Salt Test Strips

    I have an update on this issue. When I got home last night I checked the SWG and the "over salt" light had come on. I think there are two problems. First, I think the salt test strips are bad. Thanks Leslies. Second I think my pool may not be as big as I think it is.

    To make things worse, the city has just announced stage 2 water restrictions. I think this is more for the people with sprinkler systems. In 2007 there were water restrictions and I had to refill the pool after the liner was replaced. I had to get approval by the city before getting any work done. A person with the city told me that the 20k+ water it would take to fill my pool was nothing compared to the amount of water used by sprinkler systems. Maybe I could divert my return line to water my lawn for a few days.
    I got nothing right now

  12. Back To Top    #12

    Re: Acuracy of Salt Test Strips

    Quote Originally Posted by franke
    My experiance with the Compupool has been that it reads very high, however adding 840 # to a pool that I expect to be less than 2000 gals. would raise the salt level pretty high. How old are your salt strips? At the moment I am using the Taylor drop test but when I was using salt strips they both read pretty close. I would get another batch of strips or the Taylor drop test and see which reading is closer.
    Test strips are a couple weeks old. No telling how long they were sitting on Leslie's shelf. I guess I should check for an expiration date.
    I got nothing right now

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