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Thread: ? Relationship Between TDS and Hardness.

  1. #1
    DIY Junior Member sidmoore's Avatar
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    Default ? Relationship Between TDS and Hardness.

    Well, I understand that a TDS reading lumps all dissolved solids together and that these, mainly, consist of calcium and magnesium. It is also my understanding that "hardness" is a measure of the amount of calcium (mainly) in the water. What I don't understand is: How can one possibly derive a reasonably close hardness estimate from a TDS reading? Witness my latest conundrum.

    I came to realize that our water softener was no longer softening and decided that I had been pushing its capacity by running scheduled 1100 gallon cycles (this is a Culligan Twin 9100 with a Fleck controller), so, I figured a good first step was to do a few "on-demand" regens and did two for each tank. The practical result so far is the fact that the water now has that "slippery" feeling of softened water when showering. However, my pocket HM Digital TDS meter now reads about a hundred points higher (before: 640).

    So, my main question is: How useful is a TDS meter for measuring water softener performance?'

    Second, if not a TDS meter, what can I, as a homeowner, use to measure hardness?

    Thanx for listening!

    Sid

  2. #2
    In the Trades Tom Sawyer's Avatar
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    A TDS meter is pretty much usless for calculating hardness. You need a Hatch 5B kit, about 30 bucks on amazon.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Senior Member mialynette2003's Avatar
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    TDS will in fact be higher on soft water than on hard. As Tom said, a Hach 5B is a very good kit for testing hardness.

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    DIY Junior Member sidmoore's Avatar
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    Quote Originally Posted by Tom Sawyer View Post
    You need a Hatch 5B kit, about 30 bucks on amazon.
    Thanx for the tip, Tom. I had searched Hach for hardness kits and, for whatever reason, came up only with expensive, or, one shot kits. Much appreciated.

    Sid

  5. #5
    DIY Junior Member sidmoore's Avatar
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    Quote Originally Posted by mialynette2003 View Post
    TDS will in fact be higher on soft water than on hard.
    Mialynette, I had figured that might be true, but, had no way to really know, until you just verified it for me. Thanx!

    Sid

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    Water systems designer, R&D ditttohead's Avatar
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  7. #7
    DIY Junior Member sidmoore's Avatar
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    Quote Originally Posted by ditttohead View Post
    Thanx for the link, Dittohead.

    Sid

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