Adjusting pH of RO water

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BrewerDon

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In Gordon Strong's book Modern Homebrew Recipes he says that .25 tsp of 10% phosphoric acid in 5 gallons of RO water will lower the pH to 5.5.

I gave this a try this weekend and I found that it took me 1 whole tsp of 10% phosphoric acid to lower my RO water to a pH of 5.5.

Does anyone know why my results were so different? Are all RO waters not the same? Or does phosphoric acid weaken with age? Mine is about a year old.

I calibrated my meter before taking measurements and the acid was mixed well with the water.

Keep in mind, I am not discussing how grain, water, and minerals react to change pH. This question is purely about 10% phosphoric acid and its affect on the pH of RO water.

Thanks,
Don
 
A high purity RO water should have very little buffering and it probably won't take much acid to cause the pH to drop like a rock. If your water wasn't as pure as that, then its possible that it took more acid.

By the way, I don't buy into Gordon's water treatment regimen. It's the same approach that AJ espouses and it doesn't really work for pale beers without acid malt in the grist.

Water pH does not equate to producing an appropriate mashing pH. In fact, for a really pale grist that doesn't have acid malt in it, mashing with distilled or RO water will still require an acid addition to that mashing water. Adding the proper dose of acid to either of those low or no alkalinity waters will cause the WATER's pH to easily drop into the 4 range.

So don't be surprised that water pH drops really low when adding your acid dose to your mashing water. The buffering power of the grain will bring the mashing pH back into range (assuming you calculated the acid dose correctly).

PS: you can use the Water Acidification sheet in the Bru'n Water program to backcalculate what the alkalinity of your RO water actually was by knowing how much acid you added to the known water volume. It's kind of hunt and peck, but it will work.
 
In Gordon Strong's book Modern Homebrew Recipes he says that .25 tsp of 10% phosphoric acid in 5 gallons of RO water will lower the pH to 5.5.

I gave this a try this weekend and I found that it took me 1 whole tsp of 10% phosphoric acid to lower my RO water to a pH of 5.5.

10% phosphoric acid is 1.09 N to pH 5.5. That means that 1 mL of it will deliver 1.09 mEq of acid in moving something from a higher pH to 5.5. A quarter tsp is about a mL and 5 gal is about 19 L so that means that in Gordon's example the water had alkalinity of 1.09/19 = 0.057 mEq/L. As pure water has an alkakinity of 0.003 mEq/L to pH 5.5 it is plain that Gordon's water contained very little carbo (0.08 mmol/L at pH 7). The fact that it took 4 times this much for you indicates that your alkalinity is 4 times what Gordon's was in his example i.e you have about 0.32 mmol/L carbo in your water. That implies (from pH 7) an alkalinity of about 0.29 mEq/L or 14 ppm as CaCO3.

Does anyone know why my results were so different? Are all RO waters not the same? Or does phosphoric acid weaken with age? Mine is about a year old.
The answer is above. It is unlikely that your phosphoric acid has lost strength but then it probably isn't analytical grade either.

You have effectively measured the alkalinity of your RO water at 14 ppm. If your feed water's alkalinity isn't 10 to 20 times greater than that you should check you system/
 
By the way, I don't buy into Gordon's water treatment regimen. It's the same approach that AJ espouses and it doesn't really work for pale beers without acid malt in the grist.
It is quite a useful method for many (including Sierra Nevadavwho do at least some of their beers this way). There are doubtless others because if you think about it it just makes a lot of sense.

Water pH does not equate to producing an appropriate mashing pH. In fact, for a really pale grist that doesn't have acid malt in it, mashing with distilled or RO water will still require an acid addition to that mashing water.
Apparently you don't buy in because you don't understand what the approach does so let's review that. Getting a mash to the proper pH means supplying enough protons to bring each mash component that has an intrinsic pH higher than the target pH to the target pH. The components that require acid are the carbo and hydroxyl species in the water and the bases in the lower kilned malts. The proper way to calculate the acid required is to measure the alkalinity and intrinsic pH of each component and find out the proton deficit to the target pH. To do this with water we take the reported numbers, enter them into formulas (in the stickies) to obtain the acid required per liter of the water and multiply that from the number of liters of water being used for mashing. That is the amount of acid required for the water. Now you turn your attention to the malt and do the same thing there. With the water titration to a single end point is sufficient to give us all we need because we have formulae that tell us how many mEq of acid will move 1 mmol of carbo from pH1 to pH2. For the malt we don't and have to do an elaborate titration or try to deduce the malt properties from some proxy such as malt name, color, maltster etc. But we are not concerned with that here. In any case we must make a calculation of the amount of acid we need to get the malts to the target pH.

When we have the calculated amounts of acid and base we measure them out and add them to the mash or mash water.

In the Sierra Nevada/Gordon Strong/A.J. approach the single titration for the water and the ensuing calculations are skipped. The water is simply acidified to the mash target pH. At this point the water is taken care of and one can turn his attention to the grains by simply telling the calculator that the water's alkalinity is 0. Martin has indicated in other posts that he doesn't believe this to be true. He needs to think about it. We are concerned here with alkalinity to target pH - not titration end point. Once the water has been brought to target pH it needs no further acidification. No one has ever claimed that simply acidifying the mash water to target pH by itself is sufficient so perhaps Martin's misunderstanding of how the method works is based on incomplete understanding of what the method is.

As readers should appreciate the method is of great value for those that brew acid requiring beers from alkaline water especially where the alkalinity in that water varies seasonally or under other circumstances. While testing the alkalinity each day you brew is entirely feasible sending off a sample to Ward labs each time isn't and while the former is simple enough to do it isn't necessary. If you know the strength of the acid you used it's easy enough to calculate the actual alkalinity (as I did in the previous post) from the amount of acid used.


So where might this method not be applicable? The obvious example is cases where the alkalinity of the water is needed to offset large amounts of high kilned malts.
 
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fwiw, by way of contrast, it takes tenths of a milliliter of 25% PA to shift 12 gallons of the 6-8ppm TDS that comes out of my RO system from its ~6.8-ish pH down to 5.
First time I treated my sparge water from the RO system I was way the eff off with Bru'n Water (totally user error) and had sparge water in the mid-4s :eek:
Not a real problem, of course - there still was like zilch for buffering strength. I think I had used one whole milliliter of 25% PA for that precipitous drop...

Cheers!
 
fwiw, by way of contrast, it takes tenths of a milliliter of 25% PA to shift 12 gallons of the 6-8ppm TDS that comes out of my RO system from its ~6.8-ish pH down to 5.
First time I treated my sparge water from the RO system I was way the eff off with Bru'n Water (totally user error) and had sparge water in the mid-4s :eek:
Not a real problem, of course - there still was like zilch for buffering strength. I think I had used one whole milliliter of 25% PA for that precipitous drop...

Cheers!

I need to go back over all this. According to what I've got, for treating 20 gallons of TA 317 down to TA 29, I'm adding in 10 ml of 37% HCl (and some gypsum, for sulfate amendment). Compared to your use of PA, this amount of this strong acid I'm using seems insane to me. I must have something wrong.
 
I need to go back over all this. According to what I've got, for treating 20 gallons of TA 317 down to TA 29, I'm adding in 10 ml of 37% HCl (and some gypsum, for sulfate amendment). Compared to your use of PA, this amount of this strong acid I'm using seems insane to me. I must have something wrong.

No, you have it perfectly correct. The alkalinity in your water reacts with the HCl and neutralises it. In the case of RO water, little alkalinity exists to provide buffering.
Call that progress, it will make a much better beer after that treatment.
 
No, you have it perfectly correct. The alkalinity in your water reacts with the HCl and neutralises it. In the case of RO water, little alkalinity exists to provide buffering.
Call that progress, it will make a much better beer after that treatment.

OK, I thought I had missed something beyond the obvious (something beyond CaCl, CO2, and water). Easy enough for me to do. Many thanks, Cire.
 
You have effectively measured the alkalinity of your RO water at 14 ppm. If your feed water's alkalinity isn't 10 to 20 times greater than that you should check you system/

Interesting. I got my "RO" water from a machine or system at a local grocery store - Kroger. It claimed multiple stages of filtering and one of the stages clearly was reverse osmosis. Now, I am thinking that this system isn't a very good one. Last time I had my tap water tested the total alklinity - CaCO3 was 28. Since this system is starting with the same water it looks like it is not doing a very good job. I guess 39 cents per gallon was too good to be true.
 
Fourteen isn't bad for alkalinity (but then neither is 28). Also keep in mind that some operators introduce salts after the RO membrane so the water won't taste so 'flat'.
 
If the alkalinity of your water is 28 you’re wasting money on RO unless there are a lot of other issues with it.
 
If the alkalinity of your water is 28 you’re wasting money on RO unless there are a lot of other issues with it.

This is the first time that I have used all RO water. I wanted to follow Gordon Strong's recipe exactly as specified. He starts with all RO water and makes adjustments.

I like my tap water with one exception. Sulfates are high for my taste - 66 ppm. Depending on the style, I normally cut it with 0 - 50% RO water and then make adjustments.

I don't think I am wasting money on RO water.
 
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