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Thread: Anybody built an 8x40 RO?

  1. #1
    Join Date
    Mar 2015

    Default Anybody built an 8x40 RO?

    I'm curious if anyone out there has built an 8x40 RO unit for around 500-1000 taps. I'm planning to build an RO and can't fork out the money for a pre-built unit and it seems like making the jump from 2 - 4x40 membrane units to a single 8x40 unit is financially significant. What I don't understand is what the gain would be for the price paid in going to a larger unit. Anybody built one or have experience between the 4" and 8" units? Thanks for the discussion.

    2014: 12 taps, 5 gal buckets
    2015: 15 taps on bags
    2016: 150 taps: 100 on bags, 50 on 3/16" natural vac, 2x8 AUF/AOF Homebuilt Arch, 2x8 SL Drop Flu & Auto Draw, SL Propane Canner/Bottler
    2017: 225 taps: Built Lean to, Added SL hood, preheater, concentric exhaust, SL SS 7" SB Filter Press
    2018: 180 taps: Added Shurflo to 50 - 3/16", Auto fill sensor to head tank
    2019: No tapping
    2020: 175

  2. #2
    Join Date
    Jan 2016


    I've never built one, but mathematically, doubling the radius of a tube will result in increasing the available surface area by a factor of 4. In other words, a single 8" unit would have the same theoretical capacity as four 4" units. Likely there are many other complicating factors....
    55ish taps on buckets
    D&G Sportsman 18x63
    RB15 RO Bucket
    Stihl 044 and 026

  3. #3
    Join Date
    Mar 2017
    Granville, PA


    The 8" membrane will allow for higher pressure also.
    Minehart Gap Maple

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