+ Reply to Thread
Results 1 to 8 of 8

Thread: Membrane Washing: Flushing versus Backwashing

  1. #1
    Join Date
    Oct 2011
    Location
    Vermont
    Posts
    167

    Default Membrane Washing: Flushing versus Backwashing

    In reading posts on this site regarding membrane washing, I occasionally see folks use the term "backwash". I wonder are they actually backwashing their membranes, or using the term "backwash" when they actually mean "flush".

    Definitions: Backwash: clean (a filter) by reversing the flow of fluid through it.
    Flush: cleanse by causing large quantities of water to pass through it.


    Question: Do some Reverse Osmosis machines actually have plumbing set up for backwashing? This would require that the wash fluid (permeate) be pumped through the RO in reverse of its normal direction, that is pumped into the normal permeate output line.

    My assumption is that backwashing would be a more effective method of membrane maintenance than is flushing. Why are many (all?) commercially available RO units not set up for backwashing? Is it just the cost of the additional plumbing and valves? Or is there something about the membranes that makes backwashing inadvisable?

    If this has been discussed previously, someone please refer me to that discussion; my search didn't find it.

    Thanks for any replies,
    Charlie
    Last edited by CharlieVT; 08-13-2017 at 03:45 PM.

  2. #2
    Join Date
    Jan 2006
    Location
    Oneida NY
    Posts
    11,544

    Default

    I can't speak for other makes, but my owner's manual calls it backwashing, but it does not reverse the flow, it is just being flushed. One thing that does happen in the beginning of a "backwash" is that most of the sugar is washed to your concentrate tank. I suspect that is where the misnomer backwashing originated. You are washing a high percentage of sugar back where you want it, where it can be made into syrup. By the way, my RO is a Deer Run by Ray Gingerich, a basic RO.
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  3. #3
    Join Date
    Mar 2013
    Location
    Campbellford, on
    Posts
    682

    Default

    Membranes are not designed to be back washed. They have a brine seal in them which is designed to have the flow/pressure on one side and in one direction. I would think that back washing could potentially compromise this seal. I would assume when they are talking about backwash they really mean flush.
    Maple Rock Farm
    www.Maplerockfarm.ca
    400 taps on Vacuum
    18”x60” Lapierre propane evaporator with Smokey Lake auto draw off
    Homemade 3 post RO with MES membranes
    Ford TS110 tractor sap hauler

  4. #4
    Join Date
    Feb 2010
    Location
    Cape Girardeau, MO
    Posts
    125

    Default

    "when they are talking about backwash they really mean flush." When flushing,,, backwash you run the consecrate valve almost wide open to get maximum flow thru the membrane with very little going to permeate line. That washes sugar off the membrane and 'flushes' out any other stuff,,,,, only the special soap,,, acid and off season storage
    2012 200 taps on buckets,,, Built me a 2' X 11' arch,,, hope to put most on tubing next year.

    2011 100 taps on buckets, 30x 60 flat pan

    2009 63 taps on buckets,,,, 30x60 flat pan

  5. #5
    Join Date
    Oct 2011
    Location
    Vermont
    Posts
    167

    Default

    You gotta love those spell/autocorrect errors: "... you run the consecrate valve almost wide open..."
    So that's how to get the sacred syrup, run the consecrate valve wide open.

    Seriously, thanks for all the replies, Gents. The conclusion seems to be that no one is really "backwashing"; the word has just crept into the terminology of RO membrane flushing.

  6. #6
    Join Date
    Jan 2006
    Location
    Oneida NY
    Posts
    11,544

    Default

    Amen to that!
    Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
    Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
    Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
    After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.

  7. #7
    Join Date
    Feb 2007
    Location
    CAPAC MICHIGAN
    Posts
    721

    Default

    when people start using the wrong terms its impossible to know what they mean
    2x6 RAISED FLUE PANS
    by WF MASON
    650 taps on vac.
    100 on bags

  8. #8
    Join Date
    Mar 2013
    Location
    Rockport,WV
    Posts
    107

    Default

    Thanks Guys for the jibber jabber ,.... Really ... I was just thinking about this the other day and was going to ask, have been debating on doing a flush .. and seeing if the membrane is ok.

+ Reply to Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts