Did You Adjust Your New RO Filter Flow Restrictor?

Discussion in 'Reef Aquarium Articles and How To's' started by Matt Rogers, Feb 15, 2010.

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Did You Adjust Your New RO Filter Flow Restrictor?

  1. Yes

    5 vote(s)
    20.8%
  2. No

    19 vote(s)
    79.2%
  1. Matt Rogers

    Matt Rogers Kingfish Staff Member

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    If you are one of those people that likes to figure out things on your own and only glance at instructions with your new toys - you should know that you chance damaging the membrane on your new reverse osmosis water filter. It is not obvious to the naked eye, but that waste water hose you just hooked up probably has a flow restrictor in it that may require adjusting to get the desired 4 to 1 waste to product ratio.

    [​IMG]
    A Flow Restrictor from a SpectraPure ProPlus RO/DI Filter

    If you run less than a 4 to 1 ratio, not enough concentrate (water) is allowed to flow past the membrane when using your RO filter and the impurities will precipitate out on the membrane surface - clogging the RO membrane.

    To prevent clogging, "the Concentrate to Purified Water Ratio must be checked and adjusted in order to compensate for pressure and temperature variations that exist in all water supplies. The flow rate of the concentrate must be a minimum of 4X the product flow rate. (4X to 6X is an acceptable concentrate flow rate.)" - from SpectraPure's Installation and Operating Manual of a ProPlus RO/DI System

    Determining your RO water ratio is rather easy. Simply grab that measuring cup from your kitchen and time the output of your waste water for 1 minute. (you may need to dump it quick and continue to fill and measure if you have a lot of flow - or get a bigger measuring cup)

    [​IMG]
    Initial Product Output

    After you determine the milliliters from your waste water, do the same with your purified water output. Then divide the waste number by the purified product number to get your ratio.

    If your ratio is less than the 4 to 1, turn off your RO and let the pressure go down for a minute, it is time to adjust that flow restrictor.

    Carefully remove the waste hose from the quick-connect at the membrane. You should see a tip on the end of the hose like in the first picture of this article. That tip has a small hole - that whole tip is the head of your flow restrictor that has been inserted inside the waste hose.

    Now the fun part - getting that flow restrictor off. This can be rather challenging. It took this 3reefer some prying with a dull knife and a careful twist with a pair of pliers to do get it loose the first time. This process requires some delicate handling - take your time and try not to get too frustrated - you might break it.

    [​IMG]
    The Insert and Capillary Tube Removed


    Once loose, gently pull it out of the waste hose. You should see a long capillary tube attached to the insert of your flow restrictor.

    Now get out a measuring tape and refer to the Flow Restrictor Tables that should be in your instruction manual for your RO filter.

    In my case, I noted that my product water was around 154 milliliters and Restrictor Table in the manual stated that I should cut the capillary tube down to 8 inches in length.

    [​IMG]

    A new razor blade is nice to have for cutting the tube - but if you just have scissors, be sure to pinch the end of the tube back to a round shape after the cut.

    Now simply place the Flow Restrictor back into your waste hose, firmly inserting it all the way, reconnect the hose and retest your water ratios.

    In my experience, the Restrictor Tables in the manual will get you in the ballpark, but further adjustments may be required. I had to remove mine again and cut another inch off to get to 4 to 1.


    Sometimes, it pays to read the instructions! :)

    Hope this helps...
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  3. ZachB

    ZachB Giant Squid

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    Good write up.

    I didn't adjust mine, I just shoved the new restrictor down the waste hose and went from there. Seems pretty easy to adjust though. Maybe if I'm not terribly lazy next weekend I'll adjust it :)
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  4. NASAGeek

    NASAGeek Torch Coral

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    Alright.... I'll go check it...

    Thanks for the push...

    M
  5. bje

    bje Long-fin Bannerfish

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    my unit came with 0 instructions. the hoses were pre-hooked up to the unit and coiled up. ill have to try to figure out if i have a flow restrictor
  6. AZDesertRat

    AZDesertRat Giant Squid

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    Most vendors do not provide capillary tube type flow restrictors but provide a fixed type restrictor with no adjustability. The advantages of the capillary tube are that with just a couple minutes time you can trim and adjust it for a perfect 4:1 waste ratio. Understand, water temperature, water pressure and tap water TDS concentrations all have an effect on how much waste you get. With the fixed type normally found you are probably not getting 4:1, many are higher thus wasting excess water, reducing pressure available to the RO membrane which results in lower GPD and lower wate rquality. Others are not wasting enough which leads to premature RO membrane failure since it is not getting flushed sufficiently to carry the accumulated solids away, you need that velocity at 4:1 to properly do so.

    I would follow Matts directions in this thread and determine what your waste ratio is presently. If its close to the 4:1 you are fine. If its either higher or lower you should first determine what type of restrictor you have then determine what RO membarne you have, 50 GPD. 75 GPD 100 GPD etc. Flow restrictors will always be found on the waste line leading from the RO membarne to the drain. It may be visible as a white plastic tube with writing on it like 750mL (most common) or it could be mounted inside a 90 degree elbow where you cannot see it like Coralife and others provide. Buckeye and spectrapure are two vendors that provide the capillary tube type Matt pictured and it is the preffered restrictor if you are concerned about water quality, lifespan of your unit and wasting of a natural resource.
  7. Matt Rogers

    Matt Rogers Kingfish Staff Member

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    Great info. I was curious about other brands. Thank you. :thumb_up:
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  9. jdak

    jdak Astrea Snail

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    Have mine set to 2:1 for long time with no problems. Just flush it before every use.
  10. missionsix

    missionsix Super Moderator Staff Member

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    :hehe: I feel the pain. Voted no, you had me worried for a second there. My unit didn't mention anything about that in the instruction, well, I never fully read them. Just by looking at mine, I am definitely rocking a 4-6 ratio. Nice thread!
  11. AZDesertRat

    AZDesertRat Giant Squid

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    2:1 will work for awhile providing you have low tap water TDS and softened water. If not again it will work for awhile them fail quickly once the membranes fabric becomes fouled and probably ruptures. Everything will be going along fine and boom so watch out for it.
  12. MoJoe

    MoJoe Dragon Wrasse

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    I'm running about a 5:1 ratio. I contacted the company my unit is from and they said that would be fine as when it gets warmer I should start seeing the optimal 4:1 ratio.
  13. Matt Rogers

    Matt Rogers Kingfish Staff Member

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    Interesting. So should I infer that warmer water temp will result in lower ratios? Maybe I should have waited to calibrate? :p
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  15. missionsix

    missionsix Super Moderator Staff Member

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    I don't like that mine only comes out/hooks into the coldwater supply line.
  16. Matt Rogers

    Matt Rogers Kingfish Staff Member

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    I don't believe I've seen one that uses both. Perhaps the KISS principle is in play here.
  17. AZDesertRat

    AZDesertRat Giant Squid

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    Yes warmer summertime water change the waste ratio slightly. If you have big swings in water temps you may want two capillary tubes, one for summer and one for winter. If the temp variance is not that big trim it for a happy medium. I use a single restrictor here in Phoenix since our surface wate rsources actualkly don't change much winter to summer.

    It is high discouraged to hook to both hot and cold, or lend/temper your incoming water. The problem is anything over 113 degrees will damage a RO membrane. Remember being in the shower when someone flushed the toilet or started the clothes washer? You got scalded! Same thing happens with the membrane so its best to stick with cold wate ronly and boost pressure if the output is not sufficient, booster pumps are available for this purpose.
  18. jdak

    jdak Astrea Snail

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    What if you flush the membrane every time before you use it?
  19. AZDesertRat

    AZDesertRat Giant Squid

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    Membrane flush kits have no proven value. For them to provide any possible benefit you need to flush at the end of a cycle every time you make water, not the beginning but even then nothing has been documented about their benefit. I don't have one and frankly feel all they do is lighten your wallet. Keep your waste ratio at 3-4:1 and you get all the flushing you will need.
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  21. jdak

    jdak Astrea Snail

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    You don't need a kit. Just take the restrictor off the waste line. That stops the pressure around the membrane and all water is flushed through the waste line.
  22. AZDesertRat

    AZDesertRat Giant Squid

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    There is no need to do any additional flushing if you keep your waste ratio at the recommended 4:1 rate.
  23. jdak

    jdak Astrea Snail

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    But i believe it is recommended to flush before every use to "flush" the water out that has been sitting in each sump. I have officially pumped over 500 gallons of RO/DI water at a 2:1 ratio with 0ppm all the way. I do believe a 4:1 ratio isn't completely necessary and maybe a waste of water.
  24. AZDesertRat

    AZDesertRat Giant Squid

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    It will eventually catch up to you. Membranes are meant to last years not months. 18 to 36 months on average. Yours will probably be in the 18 month or less range depending on your water conditions and amount processed. More frequent membrane replacements contribute to the long term cost of ownership. If mine lasts 5+ years and yours lasts 18 months or less who has the cheaper unit 5 years down the road? Its also the cost of DI replacements too since a more efficient, read better flushed at 4:1, will produce lower final TDS and higher GPD since its surface is not fouled.
    None of the major vendors recommends flushing on start up other than to flush TDS creep away before it hits the DI. The problem is many of us automate our systems so we have no idea when they start and stop so the 4:1 waste ratio is critical to membrane life.