Maximum Pressure for RO Membrane

Discussion in 'Filters, Pumps, etc..' started by gabbyr189, Jul 21, 2012.

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  1. gabbyr189

    gabbyr189 Bubble Tip Anemone

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    So I just replaced my broken pressure gauge for my RO/DI system. Additionally, I moved to a new apartment that seems to have much higher water pressure than did my old one.

    My carbon and sediment filters are relatively new (about two months).

    The pressure gauge is reading approximately 80-90 psi with the faucet all the way on. Is this too high for the membrane? Should I turn the faucet down? Is there something else I should do to reduce it (possibly a pressure reducer)?
     
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  3. grinder37

    grinder37 Whip-Lash Squid

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    Not sure of your brand of unit,but my spectrapure unit is set up to run optimal between 40 and 80 psi,I imagine most brands would recommend similar pressures.I also have high water pressure and use a faucet adapter.I just turn my faucet on slowly and raise it up to around 70/75 psi.

    I'm thinking I read somewhere that pressure over 80psi can shorten the life of and/or damage the membrane.So yes I would turn the faucet down into the mid 70 psi range.Make sure no other water is running in the house when initially starting up,say someone is taking a shower,when they shut it off,the pressure at the faucet will rise and you could overpressurize.However after the unit is running with pressure adjusted at the faucet,flushing a toilet or something similar will drop the pressure at the faucet,but usually not enough of a drop to worry about.

    Mine will drop about 10 psi with a toilet flush,and someone getting a shower or doing laundry will drop around 20 psi,thats the reason I run in the mid 70's,so it's not overpressured or underpressured either way.
     
  4. PawPawBlenny

    PawPawBlenny Astrea Snail

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    most of the ones I've looked at have a minimum of 40 and a max of 80 and recommend around 60.
     
  5. Moby Duck

    Moby Duck Purple Spiny Lobster

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    All the comments +1

    Most operate the best at 65-70 psi and after 80 the quality starts to slip. If you can't get it To the pressure you need then you can go to hone depot and buy a regulator, just ask one of the guys there
     
  6. BuckeyeFieldSupply

    BuckeyeFieldSupply Spanish Shawl Nudibranch

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    There are a couple of issues mashed together in this thread.

    First - will 80-90 psi damage the membrane?
    No. For instance, Filmtec residential membranes are ok to a max of 300 psi.

    Next - what is the optimum pressure at which to run an rodi system? Your pressure is great. Check your waste water to purified water ratio to make sure you have about a 4:1 ratio.Your flow restrictor is sized assuming you have 77 degree water and 60 psi.

    Russ
     
  7. AZDesertRat

    AZDesertRat Giant Squid

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    The limiting factor on pressure are the fittings and housings which are rated at 125 psi.
    I run my RO/DI at 100 psi using a booster pump, the increased pressure not only increases the GPD but also improves the rejection rate or removal efficiency.
    As Russ pointed out, you may need a new flow restrictor to match the higher pressure but a capillary tube flow restrictor is a $4-$5 item.
     
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  9. BuckeyeFieldSupply

    BuckeyeFieldSupply Spanish Shawl Nudibranch

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    The clear housings we use are rated at 125 psi, but unfortunately there are many brands of clear housings that are rated much lower than 125 psi - which really makes them the weak link in terms of withstanding pressure. Some brands put out a CYA statement saying the clear housings should not be pressurized. Our fittings are rated to 230 psi at room temperature. These are two of those things that makes me cringe when I hear people say the only difference between RODI brands are the filters. Not so! But to the uninformed buyer, "a housing is a housing," and "a fitting is a fitting."

    Russ
     
  10. grinder37

    grinder37 Whip-Lash Squid

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    Ahh,my bad.I was under the impression that over the red line on the guage (80 psi) could be damaging to the membrane itself,I figured there was a little safety room figured in there,but not that much,lol.Thanks guys for clarifying.
     
  11. AZDesertRat

    AZDesertRat Giant Squid

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    Strictly liability on the vendors part.
     
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  12. BuckeyeFieldSupply

    BuckeyeFieldSupply Spanish Shawl Nudibranch

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    Your gauge likely has a red line at 80 psi because 80 psi is the maximum allowable residential pressure under the Uniform Plumbing Code.