RO water PH

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centralpabrewer

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I thought I had seen a thread recently on RO water PH, and now I can't seem to find it. I recently purchased an Express Water RO system with UV and DeIonizer. I havent used the water for brewing yet, but am getting ready to. I have check the PH of the RO water and it is near 9.5. Everything I have read says RO water should have a PH of ~7. Is it normal to have a water PH of 9.5 for RO? I have also tested in input water and the PH is near 10. I even re-calibrated by PH meter to be sure the measurement was right.
 

day_trippr

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This thread, maybe?
https://www.homebrewtalk.com/forum/threads/ro-filter-raising-ph.676892/

In any case, my well water comes out of the ground around pH 6.5, and my RO water immediately out of the system will be the same. However, the RO water pH can be shifted incredibly easily because there's essentially zero buffering to maintain its intrinsic pH. As that thread showed, just leaving RO water sitting in free air will steadily drop the pH into the 5s as it absorbs CO2...

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Silver_Is_Money

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Actually, due to the CO2 in air entering into it and reacting with it to form carbonic acid, RO water routinely has a pH in the range of 5.5-5.6.
 

Yooper

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I just checked the express Water website, and they sell an RO unit that alkalizes the water. Perhaps that is what you have.

https://www.expresswater.com/pages/ro-alkaline
Wait. This company sells an RO machine that doesn't actually give the customer RO water? They make the RO, the add minerals and alkalinity? That seems to be horribly deceptive to people who want RO water! I want to remove magnesium and alkalinity, the whole reason I bought an RO system for myself.

I guess I just never heard of "reverse osmosis alkaline system" before, but that seems really crazy. I have a RO system I bought from bulk reef supply years ago for $115 or so, and it still works perfectly for me. Drinking my coffee made with the water right now!
 

day_trippr

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It's not uncommon to find "remineralized" RO water sold, probably because frankly RO water (like distilled) is not great for straight consumption compared to, say, spring water (which has lots of minerals).

The apparent point of the paradigm is "bad stuff" is removed and only benign stuff is added back to improve palatability...

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day_trippr

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Actually, due to the CO2 in air entering into it and reacting with it to form carbonic acid, RO water routinely has a pH in the range of 5.5-5.6.
Only with actual exposure to air.
I've always found what comes out of the membrane stage of my RO system will be what went in, wrt pH.
But it immediately starts to drop if it's left exposed to the air...

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mabrungard

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Wait. This company sells an RO machine that doesn't actually give the customer RO water? They make the RO, the add minerals and alkalinity? That seems to be horribly deceptive to people who want RO water!
Couldn't we all say that we have exactly that kind of water coming out of our taps? That's what I'll do, sell a sediment filter and say that it's actually RO that's been remineralized.;)
 

Silver_Is_Money

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My local company that handles things like softeners, oxidizers, green sand filters, and the like..., and also sells RO units, asked me a few months ago if I wanted to upgrade my RO unit to one that adds back minerals. I laughed.
 

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It's not uncommon to find "remineralized" RO water sold, probably because frankly RO water (like distilled) is not great for straight consumption compared to, say, spring water (which has lots of minerals).

The apparent point of the paradigm is "bad stuff" is removed and only benign stuff is added back to improve palatability...

Cheers!
I guess that's true- but I've also seen a lot of Facebook type ads that alkaline water is for health. I've used my RO water to make coffee, and then to make seltzer. The only thing I add to my RO seltzer water is a smidgeon of baking soda, like 15 grams per five gallons, to counteract the acidity from the carbonation. I've done plain RO as my water as well, and it's ok, but the one with a tiny big of baking soda is better. I get adding minerals to try to imitate topo chico, but not for drinking water.
I like @mabrungard 's idea- let's sell tap water. It's been "remineralized for health"!
 
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centralpabrewer

centralpabrewer

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I did not get the alkaline remineralizer option. I did get the de-ionizer though. I brewed this weekend using RO water for the first time. Used BruNwater to determine salt additions, and the PH came out spot on. I was slightly over on the amount of phosphoric acid I added to my sparge water, so I added a bit of Baking Soda to boost the PH back up near 6.
 

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I did not get the alkaline remineralizer option. I did get the de-ionizer though. I brewed this weekend using RO water for the first time. Used BruNwater to determine salt additions, and the PH came out spot on. I was slightly over on the amount of phosphoric acid I added to my sparge water, so I added a bit of Baking Soda to boost the PH back up near 6.
Great! The only thing I would mention here is that you don't want to ever add alkalinity to sparge water- you want the pH to be under 6 if not using RO water, or to sparge with 100% RO water. But if the pH remained under 6, it was fine.
 

Joshuah57

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I actually do use a RO system from APEC that has the mineral ph+ option. The system fills a 4 and 14 gallon tank. Even with the option, my water still has minimal minerals. Here is a copy of my test from Ward Labs. According to the, it mainly adds a little calcium.
Screenshot_20200427-201148_Google PDF Viewer.jpg
 

Vale71

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The mineral cartridge in your system is most likely exhausted as the minerals according to the lab report are what you would expect from a system with good rejection without the mineral option. Either that or it has been assembled incorrectly.

To the original question, the relationship between source water PH and permeate PH is rather complex as H3O+ an OH- ions do interact with the membrane so one should never expect a PH of exactly 7.0 from the water as it comes out of the system. As the water reacts with the atmosphere and absorbs mostly CO2 its PH will shift towards the equilibrium value of around 5.6 but that takes time. This is all irrelevant for brewing anyway as actual mash PH will be determined entirely by grist and salt additions in any case.
 
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