TDS influenced by the source?

Discussion in 'Protein Skimmers, Mechanical Filtration' started by chas84, 17 Nov 2010.

  1. chas84

    chas84

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    Hi everyone,

    I saw a RO unit on an online auction, and asked the seller "What is the TDS of the RO water this unit produces?".

    He replied: "It is usually 0 but it depends on the source of the incoming water, because some areas the water is worst off that other places."

    This doesn't make any sense to me, as the whole point of using the RO unit is to get the water clean. Would it mean with his units one would have to run it through the RO unit more than once?
     
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  3. Manic

    Manic Moderator

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    Most RO membranes are only 95-99&% effective. So for example 100TDS incoming water will come at say 1TDS but 200TDS water will come out at 2TDS. That is why you use DI Resin after the membrane to make it 0 TDS all the time.
     
  4. chas84

    chas84 Thread Starter

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    Thanks Manic. Makes more sense now.
     
  5. Rory

    Rory Admin MASA Contributor

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    As the RO membrane becomes more "clogged" it will end up producing higher TDS water and at some point you will need to replace it. Also the DI resin can only absorb a certain amount so will also need to be replaced once it's "done". Obviously with the above, the dirtier the water the shorter the RO and DI will last. You could also put the water through DI only but at 100TDS it will last 1/100th as long as water that's gone through RO and is at 1TDS.
     
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