Why use a booster pump on your RO or RODI system?

Discussion in 'SpectraPure' started by SpectraPure, Sep 17, 2009.

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  1. SpectraPure

    SpectraPure 3reef Sponsor

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    Another perspective on Booster Pumps...
    Another perspective on Booster Pumps for RODI systems

    We often are asked the questions, “If you operate your RODI system at less than optimum tap water pressures, what is the downside? Is there a negative?”

    To help answer these questions, I have provided data (below) that shows the actual results of various pressures applied to a typical RO membrane.


    Membrane Pressure GPD Measured % Rejection % Increase
    35 39.3 97.5
    45 55.2 98.2 0.7
    55 67.9 98.3 0.8
    65 81.8 98.3 0.8
    75 97.7 98.5 1.0
    85 111.5 98.7 1.2

    Note: 80.8 F, .932 TCF, 950ppm TDS, 1150 uS,
    OPCF 7 psi; corrected psi 67


    Generally speaking, production rate is directly proportional to operating pressure. It can be seen in this example that raising the pressure by the use of a booster pump from 35 pounds (a commonly found pressure in many homes and offices, especially as demand fluctuates during busy periods) to 75 pounds increases production rate by a whopping 2.5 times! This is the primary and most common reason for adding a booster pump to your system (either an RO or an RODI system)
    you want to make more water faster! In cold-water locations, a booster pump can also increase the production rate, as production rate is proportional to water temperature.

    Another reason for booster pumps that is often over looked, is that in hard water locations (many places in the country) % rejection improves significantly with the increase in pressure provided by a booster pump. Our data above shows a rejection performance increase from 97.5% to 98.5%, or about 1%. How important is 1%? The rule of thumb for DI resin capacity is for every 1% RO membrane rejection improvement you get a 25% increase in DI cartridge life (due to the reduced ionic load). Thus, with this particular RO membrane as an example (they do vary somewhat), you can see that operating an RODI system at higher pressures (75 psi) will gain a 25% increase in cartridge life over lower pressures (35 psi). In other words, with a 25% gain, every fifth DI cartridge is free! As DI cartridge changes are a significant cost of producing DI water over the life of your system, a 25% increase in cartridge life can add up fairly quickly.

    bruce
     
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  3. Otty

    Otty Giant Squid

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    I run one and notice a big difference in output from unit.
     
  4. =Jwin=

    =Jwin= Tassled File Fish

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    We have one for our RO unit. A good buy, IMO :)
     
  5. sailorguy

    sailorguy Torch Coral

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    Just a couple questions,1) Does the increased pressure effect the amount of waste water? 2)Does it effect the D/I function? I currently use a tap water D/I filter,API,and it requires that the water pass thruogh it slowly to work effectively.Does adding a pump to RO/DI unit add pressure and not increase the volume of water passing through the D/I cartridge? I have been wondering about this for a while,thanks,Dave
     
  6. SpectraPure

    SpectraPure 3reef Sponsor

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    1) Increasing the pressure requires adjusting the flow restrictor to maintain the 4-to-1 ratio the membrane needs to keep clean.

    2) DI function may improve a bit because higher pressure makes slightly more pure water, making the DI last longer.

    3) Adding a pump increases the pressure on the membrane and increases the volume of water passing through the DI cartridge. Not a problem for our DIs. It can be a problem when trying to pass tap water through DI because there is so much more hardness to be neutralized, requiring a much longer "dwell time".

    Scott
    SpectraPure, Inc.
     
  7. Av8Bluewater

    Av8Bluewater Giant Squid

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    Do you guys sell booster pumps? If so gotta link?
    Thanks for the info.
     
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  9. SpectraPure

    SpectraPure 3reef Sponsor

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  10. grubbsj

    grubbsj Gigas Clam

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    OK, I'm running a 75 gallon/day, 5 stage RO/DI system, which gets between 42 - 45 PSI at the inlet of the RO filter... On average, the system is on-line for ~4 hours/day (10-12 gal/day), to maintain a 75 gallon tank full.

    I could see using a booster pump for the increased efficiency, but increased capacity is not needed. My question is if the increase in efficiency alone (saving money on DI resin replacements) would be sufficient to cover the cost of the pump & ??? necessary to make the change to the system during the useful life of the pump.

    Thanks, Joe
     
  11. SpectraPure

    SpectraPure 3reef Sponsor

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    Going by the typical numbers in the table above, you can see that the purity increase from 45 to 75 psi is 1%.

    Scott
    SpectraPure, Inc.
     
  12. SpectraPure

    SpectraPure 3reef Sponsor

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    ...and 2% is a a doubling of your DI life.
    bruce
     
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