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Thread: RO pH flucuations

  1. #1
    Join Date
    Jun 2014
    Location
    United States
    Posts
    9

    RO pH flucuations

    First off, my biggest problem is my RO plant, I'm trying separately to sort that already.

    When I started off here 3 months ago the RO pH was 5.5 to 5.6 at 5-10ppm, which made for easy salt additions and consistent pH. For some unknown reason, one day the pH jumped up to 6, while the ppm stayed the same. I've tweaked the salts to try to bring up the RA more, but on my highest selling wit I am now ending my boils around 5.7, from 5.4 previously. Luckily the post-ferm pH is still 4.4-4.5, which is high but acceptable in a beer that sells out in 4-5 days.

    My RO water is right now consistently 6.0-6.2. This is India, so the plant is for the entire restaurant and bar...so I have input to make changes to the plant but I do not run it.

    I recently started adding 85% phosphoric to my HLT at the beginning of the day and after re-filling it for sparge. I added 20ml to 1500L yesterday and my wit's first runnings were still 5.9. I added another 20ml to the sparge water and 20ml directly to the kettle. My kettle full was 5.8, my post-boil 5.7 and my last runnings 6.2. I'm not a big fan of acid additions, but should I try adding more acid, add some acidulated malt, up my Ca and Mg additions, or remove all of the carbonates from my salt additions?

    My current wit water additions in ppm, and all of my salts are added to the mash strike water. Grain is milled into bags and then dumped in after the tun is at full fill and manually stirred.
    Ca- 80
    Mg- 3
    SO4- 56
    Na- 15
    Cl-93
    Bicarb- 65, as 0.03 g/l CaCO3 and 0.04 g/l Baking Soda
    RA- neg 4

  2. #2
    Join Date
    Nov 2010
    Location
    Carmel, IN
    Posts
    40
    Water with very low TDS (like RO water), gives pH meters difficulty in measurement. I'm not really surprised that the pH reading is varying. But a more important fact is that the pH of your water source has little effect on its performance in brewing. The buffering of the mash system does overwhelm the effect of pH in low TDS water.

    Given that, I'd ignore pH and keep a close eye on the TDS content of your RO treated water. If TDS rises, its a sign that the membrane performance is failing. Do be aware that a RO system can spit out a burst of high TDS water if the system is idled and restarted. Regular operation should keep that burst of TDS from occuring.
    WaterEng
    Engineering Consultant

  3. #3
    Join Date
    Jun 2014
    Location
    United States
    Posts
    9
    Thanks, I've already toned down my salt additions to bring my lighter beers to a RA of about -30, so far it has helped a bit. I've also started treating only the sparge water with acid. I think part of my problem was a poor vendor adultering their products and then sealing them up (India). I got a proper bottle of 85% Phosphoric and now it takes about 2 mL to get my sparge water from 6.2 to 5.7.

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