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Thread: RO UNITS: QUESTIONS AND ANSWERS

  1. #1
    Registered Member RandalB's Avatar
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    Default RO UNITS: QUESTIONS AND ANSWERS

    Hi all,
    Feel Free to ask your Reverse Osmosis questions here. Anything about RO and RO/DI units, equipment and accessories is fair game for this thread.

    So if you have a question about anything RO related (except water chemistry! That's for the main section of Water Works) feel free to ask and I'll do my best to answer it for you.

    FIRE AWAY!!! ;D
    RandalB

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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Here is a question I've never been able to get a consistent answer on...


    Does R/O remove chlorine from the water?


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    Registered Member RandalB's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Jeff,
    Actually the RO membrane does not remove the chlorine. The carbon block prefilters remove the chlorine before it reaches the membrane.

    RO membranes (TFC) are sensitive to Chlorine and are easily and quickly damaged by it. That's the reason the carbon block filtration is necessary.

    In answer to your question; RO units remove chlorine from the feed water. Both the product water and the waste water have no chlorine in them.

    HTH,
    RandalB

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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    I produce around 25 gallons per day. Based on that usage, how often should I replace the membranes?

    I'm using the Kent Marine RO100TFC.

    Do I need to replace the pre-filters as well?

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    Registered Member ronrca's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    I do have a few questions a perhaps there are others that may have the same questions.

    Its about the parts like booster pump and flush valves! What is their function? What are the effects of adding them or not adding them to the RO unit?

    Thanks! ;D

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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    I know the booster pump will give you more output if you have a low pressure situation. If your tap pressure is good, you probably don't need the booster pump.

    As far as the flush kit, I don't know exactly how it works, but it is supposed to make your membrane last longer if you have hard water.

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    Registered Member ronrca's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Thanks Jeff!

    The questions now are:
    How do you know if you need a booster pump (how do you know if your pressure isnt enough)?

    What is considered 'hard' water?


  8. #8
    Registered Member RandalB's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Jeff,
    Booster pumps are also effective in countering the effects of low temperature feed water for those of us who's tap water goes below 45 F in the winter. Even if you have 50-60PSI normally, you can loose up to 50% of your production when the water gets colder.

    You should replace Membranes every 2-3 years or when they fail.

    Prefilters should be replaced according to the manufacturer's instructions.

    On my units you replace them when they clog or according to the following schedule based on the TDS of your feed water:

    TDS: Replace every:
    0-200 6 months
    200-400 3 months
    400-600+ Monthly or as needed

    If the TDS of your product water goes up abruptly or your Water production drops off, it may be time to replace the prefilters.


    Ron,
    The Booster pump is for Low pressure or Low temperature feed water (or both) It increases the line pressure to 100PSI which has the effect of increasing the efficiency of the RO membrane. This overcomes the loss of production that comes from low temps and pressure.
    Most RO membranes are rated at 50 or 60 PSI. If your tap water is at 40 PSI your RO unit will produce less water than rated. The membrane is also rated at 78 F. Below that, the unit will produce less water than rated. So if your water is 40 PSI at 45 F, your unit will produce 35-50% of rated GPD. Your waste water production will also increase dramatically. In some cases up to 10:1 Waste to product. This is directly related to your Pressure and temp.

    So, adding a booster will:
    Increase the line pressure
    Increase the production of the RO unit up to 60%
    Increase the efficiency of the RO unit (less waste water) up to 2.5:1 waste to product
    Decrease the TDS of the product water (unit filters better)

    Do you need a booster pump? Ask yourself:
    What is my tap water pressure? (you can get a cheap test gauge at home improvment stores) If it is below 40PSI, you need one.
    How cold does my tap water get? If it's below 50F in the winter, a booster will be beneficial and save you $$.

    The flush valve is simply a bypass of the flow restrictor that allows water to run quickly over the surface of the membrane flushing away the calcium/magniesium crust and bacteria that builds up on the surface of the membrane. This is essential to the long term life of the membrane. It should be done at least monthly to weekly depending on the TDS of your feed water. A valve is opened and the water is allowed to flow for a minute or so and then the valve is closed. Units without a flush valve can be flushed by removing the flow restrictor from the waste line and allowing water to run through the unit.

    The TDS of the water makes no difference on the need for membrane flushing. All RO membranes need to be flushed periodically due to buildup.


    Now we're seeing some action in here! Keep 'em coming!
    RandalB

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    Registered Member ronrca's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Thanks Randal!

    Anothe question! You mentioned using cold water thus losing efficiency! What about using hot and cold water mixed to get the temp back up around 80F?

  10. #10

    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    A few questions I've been thinking about -

    If I have well water - the carbon block isn't needed to remove clorine , so is it then worthless?

    I have a water softener and well water, so no clorine or cloramines and soft water - what extra could or would an R/O do ?

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    Registered Member RandalB's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Stilllearnin,
    If you have well water the carbon block catches some of the dissolved solid material and naturally occuring organic chemicals in the water if they are present. The carbon block is not critical in well water but still a good precaution.

    The definition of soft water VS Hard water in a home water filtration system is different than soft water as defined in discus keeping. Soft water in your home has all the magnesium and calcium content exchanged for sodium content this is defined as "Soft" in the water filtration sense. There is a high sodium content to the water that can be detrimental to your fish. When referring to "Soft" water in discus keeping, it refers to water with a low Total Dissolved solids or conductivity. So "Soft" water in a discus keeper's tank has very little dissolved mineral content and very little general and carbonate hardness.

    Your sodium rich "Soft" water from your home water softening unit is ideal for RO unit use as there is no Calcium and Magnesium content to damage the membrane. The unit would perform better as sodium ionic content is easily removed by the RO.

    Hope that wasn't confusing,
    RandalB

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    Registered Member ronrca's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Quick question! Lets say that I only have a 2 stage unit! How difficult would it be to change that into a 3 or 4+ stage unit?

    What about adding a 2nd or 3rd membrane to increase output? Does it work that way?

  13. #13
    Registered Member RandalB's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Ron,
    The bad thing about the 2 stage units is the very low capacity prefilters they use. With that in mind, you don't want to add additional membranes to a 2 stage unit, too easy to damage the membranes.

    Upgrading a 2 stage to a 3 or 4 is fairly easy, the only component you will use is the membrane housing. You just need the lower prefilter assembly and the proper connections.

    RandalB

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    Registered Member ronrca's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    So, if you want to add another membrane, you would also want to add another prefilter?

    The RO unit I have has 2 prefilters, polystuff and carbon block and 2 membrances (100gpd each=200gpd)! I have seen units with 3 and 4 prefilters. Is it worth to add more prefilters like another polystuff perhaps with a different micron rating?

    Another quick question! You see 2 stage RO, 3 stage, 4, 5, and 6! Does the number indicate how many prefilters? For example a 2 Stage, is it a polystuff prefilter, a carbon block and membrane or just carbon block and membrane?

    Thanks!

  15. #15
    Registered Member RandalB's Avatar
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    Default Re:RO UNITS: QUESTIONS AND ANSWERS

    Ron,
    Make a guy a mod and he's full of questions! HA HA.

    For your First, what's the TDS of your water? Additional prefilters are to give protection to the membrane in high TDS feed water. Additionally, a second carbon block can be added if you have a lot of chlorine or chloramine in your water. So if you have real crappy feed water, it may be in your best interest to add additional prefiltration. Or just don't worry about it, I sell membranes real cheap.

    Second,
    The stages of an RO unit indicate how many filter elements the water passes through when processed by the unit. A 2 stage unit has 1 prefilter (carbon block or inline GAC filter) and a membrane. You have a 3 stage unit. Poly prefilter, Carbon Block and Membrane (I don't count the second membrane as a stage, some do though.)

    I am working on a total for your order, I'll send it through shortly.

    RandalB



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