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Thread: Refractometer and Salinity Measurements are unexpected...

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    Refractometer and Salinity Measurements are unexpected...

    Question,

    I'm using my refractometer http://www.google.com/url?sa=t&sourc...qG8NtsQFuD1iPg from my SW reef tank to measure the Salinity in my Pool. I also checked the calibration of the Refractometer this morning.

    What's weird, is I'm getting a 5PPT (5000ppm) reading - considering I only added (for the first time) about 2PPT last weekend - and then just finished draining 1/2 the pool cause my CYA was still well over 100 - for the life of me, where is this salt reading coming from? This is weird, because a refractometer is supposed to be "spot-on".

    Other than "best guess" (I put XXX lbs of salt in YYY pool) - what other methods are people using to measure Salt?
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)
    CAPTAIN JAMES T. KIRK: "I'M SORRY. I CAN'T HEAR YOU OVER THE SOUND OF HOW AWESOME I AM" (Thanks to TFP!)

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    Re: Refractometer and Salinity Measurements are unexpected...

    Answering my own question here...

    My Jandy AquaPure (just got it running...) says I have 1.9GPL (1.9PPT) and need to add to 3.0GPL.
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)
    CAPTAIN JAMES T. KIRK: "I'M SORRY. I CAN'T HEAR YOU OVER THE SOUND OF HOW AWESOME I AM" (Thanks to TFP!)

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    JasonLion's Avatar
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    Re: Refractometer and Salinity Measurements are unexpected...

    I recommend Aqua Chek Salt Test Strips.
    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: Refractometer and Salinity Measurements are unexpected...

    You can measure salt levels with a refractometer? I guess there are more than one kind of refractometer. They are used to measure sugar. I use one for brewing wine and beer to check the Brix (gravity) of my Wine Must or Beer Wort. I have only seen refractometers that have wither a Brix or Specific Gravity scale to view.
    18 ft.52" Round Atrium AG -7600 gallons, Sand Filter, Vinyl liner, Royal Entrance Steps, 80 lbs.solarsalt

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    Re: Refractometer and Salinity Measurements are unexpected...

    I am also a reefer and I'm putting in my first SWG. I love this site!!

    I think I've got this figured out, as I'm inclined to use my refractometer as well.

    The refractometer gives the specific gravity, in

    (grams of sample) / (grams of pure water), or grams/grams, so unitless.

    Water with solute dissolved in it will have greater mass than an equivalent volume of pure water, so the number is >1.

    For reef tanks, its about 1.0025, roughly sea water.

    In other woords, 2.5 thousands of a gram of salt are dissolved in every gram of water.

    Or, 2.5 grams of salt per 1000 grams of water.


    THe recommended salinty for our aquarite pools is about 3000 ppm (parts salt per million total parts, and since there is so little salt relatively speaking, it is really parts salt per million parts water).

    3000ppm is really 3000 grams salt per million grams water.

    3000/1000000= .003

    Use your refractometer and adjust the water to 1.003.


    Having said all that, I will be getting test strips for doulbe check. If they are different, I won't be sure which to believe. THe refractometer is supposedy dead on accurate once calibrated with distilled water. . .
    1) The size of your pool in gallons about 38000 gal, 20x40", about 8 ft at deepest.
    2) The type filter you have (sand, DE, cartridge) sand
    3) If your pool is an AG (above ground) or IG (in ground) IG
    4) If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass Plaster
    5) If you know, tell us the size pump and the size (flow rate) of your filter. ? I do have a polaris accessory pump for the sweeper.

  6. Back To Top    #6
    Guest

    Re: Refractometer and Salinity Measurements are unexpected...

    Been doing reefs since the 70s when there was very little info on them so my knowledge of them is probably on par with my knowledge of pools. Have used refractomers, hydrometers of various types, and conductivity meters. For tanks I prefer a large sized glass hydrometer. For pools I prefer the strips or (If you REALLY know how to do it properly) a titration test for chloride ions.
    IF you have a LOT of tanks (in my heyday I has 9 going at once) or a lot of pools to monitor such as a pool supply store service tech (been there and done that too) then I would have to say the conductivity meter is the best choice BUT it does need to be calibrated readily with the proper standard solution)

    My 2 cents.

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    Re: Refractometer and Salinity Measurements are unexpected...

    Oh-oh-oh-oh... I have a Lamotte Chloride kit from my Discus days (wow, that was a while back). What Chloride reading should I be looking for (if the reagents are still good). My Jandy says I'm at 3200ppm, but my feeling is that it's just a conductivity reading/interpretation - not that it matters much. I also have a conductivity meter from the discus/angel freshwater period (now I have a 125G FW planted, and a 20G "mini" reef that won't die).

    In the '90s, I had over 1000g of tanks in the basement in the 'burbs of Chicago and so many angelfish I had every store and wholesaler stocked within a 50 mile radius - and was still flushing them .

    Now, if I even mention the word "discus" around the house, the wife glares... (feels eyes on back of head)

    - Jeff
    ~45Kg Pool with attached Spa, NSP-72 DE, Minmax 400 Heater, Tahoe Blue Pebbletech, Jandy SWG via Aqualink RS-8, The Pool Cleaner (black)
    Pumps: X3 Hybrid Pump (switches to SPA), 2HP Spa (additional, when SPA is on), and a 1HP For Waterfall
    8, 4x12 Solar Panels on the roof of the pool-house (~12' up)
    CAPTAIN JAMES T. KIRK: "I'M SORRY. I CAN'T HEAR YOU OVER THE SOUND OF HOW AWESOME I AM" (Thanks to TFP!)

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    Guest

    Re: Refractometer and Salinity Measurements are unexpected...

    Quote Originally Posted by taekwondodo
    Oh-oh-oh-oh... I have a Lamotte Chloride kit from my Discus days (wow, that was a while back). What Chloride reading should I be looking for (if the reagents are still good). My Jandy says I'm at 3200ppm, but my feeling is that it's just a conductivity reading/interpretation - not that it matters much. I also have a conductivity meter from the discus/angel freshwater period (now I have a 125G FW planted, and a 20G "mini" reef that won't die).
    I would doubt it is still good. I use a Taylor chloride test kit (sllver nitrate titration with chromate indicator) but it is a PITA. I prefer the strips, which are actually capillary titrators.and use the silver nitrate without the chromate indicator. Both are calibrated to express the results in ppm but chloride and conductivity are not going to be exactly the same. However, they are close enough for government work!) If your conductivity meter is not set up to read in ppm or ppt salt (needs an adjustable correction factor built in to do it right) then it will probaby be a PITA to use also.

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    JasonLion's Avatar
    Join Date
    May 2007
    Location
    Silver Spring, MD
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    Re: Refractometer and Salinity Measurements are unexpected...

    brackishpoolboy, welcome to TFP!

    I think you added an extra zero in one of your numbers. Ocean water varies somewhat, but is typically around 35 ppt (parts per thousand), which would be a specific gravity of 1.0264 and a refractive index of 1.3394. Water for a SWG is usually around 3 ppt salt, which would have a specific gravity of about 1.0023 and a refractive index of about 1.337.
    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: Refractometer and Salinity Measurements are unexpected...

    Quote Originally Posted by JasonLion
    brackishpoolboy, welcome to TFP!

    I think you added an extra zero in one of your numbers. Ocean water varies somewhat, but is typically around 35 ppt (parts per thousand), which would be a specific gravity of 1.0264 and a refractive index of 1.3394. Water for a SWG is usually around 3 ppt salt, which would have a specific gravity of about 1.0023 and a refractive index of about 1.337.
    I stand corrected. My refractometer has both ppt and sg, and agree with your numbers.
    1) The size of your pool in gallons about 38000 gal, 20x40", about 8 ft at deepest.
    2) The type filter you have (sand, DE, cartridge) sand
    3) If your pool is an AG (above ground) or IG (in ground) IG
    4) If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass Plaster
    5) If you know, tell us the size pump and the size (flow rate) of your filter. ? I do have a polaris accessory pump for the sweeper.

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