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Thread: RO Unit Components: Basic Assembly

  1. #1
    Registered Member RandalB's Avatar
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    Default RO Unit Components: Basic Assembly

    Hi All!

    Due to an overwhelming demand, myself and the Simply Discus Team present the first in a series of RO unit education threads.

    In this thread I will walk you through some of the basic components that I use when assembling an RO unit and what they are used for.

    Please hold questions/comments until the end of my posting, as I will be doing my W/C's while I am doing this thread. After that, feel free!

    RandalB

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    This particular unit was assembled for a fellow Moderator, Ralph. It is a 5 stage RO/DI unit. The abbreviation RO/DI stands for Reverse Osmosis/Deionization. This particular type of water filtration unit is designed to remove ALL dissolved solid/ionic content from the feed water, leaving the product water's Total Dissolved Solids at 0 PPM.

    When I refer to 5 stages, in this case they are:

    1) A 5 micron Polypropylene Prefilter (Sediment/Debris Removal)

    2) A 1 Micron Carbon Block Prefilter (Dechlorination/Bacteria removal)

    3) A Dow Filmtec 1800 series Residental Reverse Osmosis element, 75 Gallons Per Day rating

    4) A Dowex C100E Mixed bed (cation/anion) deionization resin cartridge

    5) A Granulated Activated Carbon Polishing Filter

    In this case the 2 prefilters do the job of removing most of the debris and bacterial content of the feed water and perform the critical task of removing water treatment chlorine from the feed water. As you may or may not know, chlorine destroys RO membranes very quickly.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    Here is a photo of the 3 Filter cannisters that will be used in the construction of the unit. The First two from the left will be prefilters and the last one, the DI unit. These canisters are standard 10" which means they are designed for 9.75" filter elements. 9.75" is industry standard.

    Note the use of clear canisters, which allows the user to monitor the condition of the prefilters/DI.


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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    The cannisters are placed in order and the feed ports are lined up so the input and output sides are matched properly. (outputs connected to inputs).

    Next, I use teflon tape to wrap the threads of all the fittings that will be used on the unit. I use John Guest Speedfit (tm) fittings on all aspects of the RO unit. This type of fitting allows quick assembly and ease of maintenance. The Tape keeps the fittings from leaking.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    Next,
    the fittings are attached to the prefilters cannisters with a wrench. Straight fittings are used for the First feed connection and the last filter connection because they will be fitted with 180 degree rotatable fittings for ease of installation by the user.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    Next,
    A white powder coated steel bracket is screwed to the top of the cannisters, providing stability to the cannisters and support for the upper stages. Additionally, two Membrane housing clips are attached.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    Here's a top view of the attachments. Note the angled fitting for the DI unit coming through a gap in the bracket.
    The screws being used are stainless or galvanized for protection from rust.

  8. #8
    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    Next,
    The Membrane. The most important and expensive part of the unit, the membrane provides filtering action down to the atomic level.

    Standard TFC (Thin Film Composite) Membranes have holes that are between 200 and 400 Atomic mass units (1 Neutron=1 AMU). These tiny holes allow water, H2O to pass while trapping larger molecules on the surface of the membrane where they are washed away by waste water.

    I personally recommend DOW Filmtec membranes. As the originator of the technology, Dow provides the most efficient and effective membranes on the market today.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    There are two sets of seals on the membrane that are lubricated with silicone lubricant prior to being installed in the membrane housing or vessel:

    A double set of O rings, on the product water end, keep the product and waste water from mixing.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    And a larger Flanged O ring that keeps the element centered in the housing. Note the hole in the plastic stem. Once the membrane is in the housing, these holes are used to remove it for replacement using a piece of string or wire.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    The product end of the membrane (2 O rings) is inserted first in the housing.

  12. #12
    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    The membrane is then slowly and gently seated in the housing to avoid damage to the O rings.

  13. #13
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    Default Re:RO Unit Components: Basic Assembly

    The housing is then capped and tightened with a wrench. The cap is on the feed water end of the housing.

  14. #14
    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    The Membrane housing is attached to the mounting bracet with the previously attached clips.

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    Registered Member RandalB's Avatar
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    Default Re:RO Unit Components: Basic Assembly

    One of the cheapest but most important parts of the RO unit is the Flow Restrictor. Without it, the unit doesn't work. The flow restrictor provides the pressure that makes the unit work. Flow restrictors are precision calibrated to allow only a certain amount of water to pass in a set time period. If improper sizes are used, the unit will not have enough pressure to push water through the membrane or will not have enough waste water flow to keep the membrane clean of contaminants.

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