RO filter ( reverse osmosis ) ?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by tommy vercetti, May 5, 2009.

  1. tommy vercetti

    tommy vercetti New Member

    May 5, 2009

    I used to have an RO filter I used for making pure water for my aquarium. Recently I decided to install one for drinking water. Luckily I got one free on craigslist. I plan to replace the membrane, and postfilter.

    Now the old RO unit I had didn't have a pressure tank. I just let it slowly fill a 5 gallon water jug. I had to watch to make sure I didn't waste good water, but I knew the approximate time it took to fill.

    Also the old one had a "backflush" feature where I could apply back pressure to the filter and "clean" the membrane.

    I currently have two "prefilters" already working as my drinking water filter connected to a standard drinking water faucet. One filter cartridge is foam and the other one carbon. I plan to use those as my prefilters with the RO unit.

    Now to the questions:

    1. Why can't I use my current drinking water faucet? The RO one is complicated with 3 tubes coming out and I don't like the look as much. I don't understand why it needs so many tubes just to dispense water.

    2. Why doesn't the new RO unit include a backflush option? Does it need it?

    3. What is the purpose of the "postfilter?" It seems like it should come out of the RO membrane pure enough...why one more filter?

    4. The storage/pressure tank is new to me. It has an inflation nozzle, and a recommended pressure. Do I pump it full of air after I plumb it and turn the water on? Is there any way to clean the inside of one of those?

    Thanks a lot!
  2. Redwood

    Redwood Master Plumber

    Dec 15, 2007
    Service Plumber
    One of the tubes is for turning the water on an off
    The other 2 are for the drain which includes an air gap in your faucet.

    The flushing is a desireable feature to flush the membraine clean

    To help maintain purity and good taste.
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  4. Gary Slusser

    Gary Slusser That's all folks!

    Aug 31, 2004
    Wherever I park the motorhome.
    That's IF you have an air gap type faucet. If not one line is to drain, one to the tank and one from the water line to the RO's inlet fitting.

    And actually, with an air gap faucet, you have a drain line from the RO to the faucet and then from the faucet to the sink drain, and the one from the RO to he tank and one from the tank to the faucet. So there is an additional piece of drain line but the same 3 lines to/from the RO.
  5. 99k

    99k Radon Contractor and Water Treatment

    Aug 16, 2008
    Contractor of Radon Reduction, Testing, and Water
    Fairfield Co.,Connecticut
    The post filter is associated with the holding tank. When there is a demand for water, the staged water in this tank is delivered to the last carbon filter to "polish" and remove any tastes from the tank. The pressure should be around 10 PSI and set-up before the system is put into service. On a yearly basis, remove all filters and add a bit of bleach to the stage 1 sump. Run the system to disinfect the entire system (which will take care of the tank). Once completely flushed, reinstall the membrane and change the sediment and carbon filters.
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