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Old 05-08-2011, 12:48 PM   #1
VikeMan
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Default Distilled Sparge Water and pH

Let's say you hit a perfect 5.2 (or 5.4) mash pH. Then you sparge with distilled water. As I undersatnd it, pure distilled water 'has no' pH. So how does it change the pH of the wort? TIA!

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Old 05-08-2011, 01:01 PM   #2
onthekeg
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It has no buffering capacity, so it won't change the pH of your wort to any appreciable degree.

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Old 05-08-2011, 05:27 PM   #3
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Quote:
Originally Posted by VikeMan View Post
Let's say you hit a perfect 5.2 (or 5.4) mash pH. Then you sparge with distilled water. As I undersatnd it, pure distilled water 'has no' pH. So how does it change the pH of the wort? TIA!
By dilution. Let's say you squeezed all the liquid out of the mash with some magic centrifuge or Strainmaster or some similar device. Now take a liter of that wort and start diluting it with DI water. When you add the first cc you won't see much of a pH change. When you have equal parts of wort and DI water you will see a little. The acidifying stuff in the wort is now at half the concentration it used to be. Now keep adding. By the time you get to 3 or 4 liters DI water and 1 liter of wort the acidifying stuff is pretty dilute and the pH will have risen appreciably towards that of the DI water. It should be clear that if you went to 100 parts DI water to 1 part wort that the wort would be of little significance and the pH would be close to that of the DI water. DI water does have a pH usually around 6 or so if it has been exposed to air. DI water which has been protected from air has a pH of 7. What it does not have is buffering capacity (alkalinity 2.5) to speak of.

You don't, of course, dilute that much in actual sparging and you should be able to get away with DI sparges down to 3 °P runoff or so without busting 6. The wort is a buffer system and buffer systems resists pH change from dilution (but are not totally immune to them) and other stresses. DI water doesn't constitute much of a stress.
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Old 05-08-2011, 05:50 PM   #4
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Sparging with distilled water would eventually exhaust the 'acidity' of the mash and raise the mash pH above the desirable 5.4 target. But as mentioned above, you would have likely exhausted the sugars from the mash. Using the typical minimum runoff gravity target of 2 to 3 P will avoid the possibility of pH rise when sparging with distilled water.

I had previously been recommending that all sparging water should be brought to a pH of 5.5 to 6.0 in Bru'n Water, but I finally came to the conclusion that its alkalinity in sparge water that needs to be controlled and that pH was actually less of a concern.

Since more brewers have (or should have) the ability to monitor pH, pH is still the easiest way to monitor the alkalinity reduction in sparge water. Therefore, I revised the sparge water acidification in Bru'n Water a few months ago to target a maximum alkalinity of about 20 ppm (as CaCO3) as a more appropriate goal. Users of Bru'n Water now see the resulting alkalinity of their acidified water. It turns out that waters that have natually low alkalinity may only have to be acidified to a pH of maybe 6 while a high alkalinity water may have to be acidified to 5.5 to reach the 20 ppm alkalinity goal. As AJ points out, distilled water users don't need to do anything to their sparge water to achieve the 20 ppm alkalinity goal.

Enjoy!

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Old 05-08-2011, 07:03 PM   #5
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I'm a little confused by all of this.

I do BIAB and I do either 2 or 3 batch sparges depending on needed volumes, etc.

I am using distilled water for a brew on Monday. This will be the second time I've used distilled water. With my first distilled water batch I added salts to the mash water with good results. I also added salts to the sparge water but did not add CaCO3 because, if I remember correctly, Briggs suggests avoiding bicarb in the sparge (I think he said because of astringency issues?). The sparge water salts were for a combination of pH and overall water profile levels (Mg, Cl, SO4).

Some people seem to be suggesting to not add salts to the sparge?

But it seems to me that with batch sparging, the distilled water will greatly overwhlem the amount of mash water and therefore the pH will essentially be that of pure sparge water. Is this ok? What about pH of the boil and what about Mg, Cl and SO4 levels in the boil after collecting mash and sparge water? Will the pH of the boil be ok because the mash water will determine the pH???

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Old 05-08-2011, 07:17 PM   #6
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You are right in your surmise that if there is enough DI water the pH of the mix will be that of DI water but as I stated in my earlier post you will not have nearly enough sparge water for that to happen.

As I also stated in my earlier post, DI water has very little buffering capacity. It only takes ~0.001 mEq of acid per liter to lower the pH of DI water to 6. That's so little that the carbon dioxide in the air (0.03%) is enough to do it. There is quite a bit more acid than that in mash. Yes, eventually you can wash it all away and the pH will rise but a noted here and previously if there is enough extract remaining to measure 3 °P there is enough acid remaining to keep pH < 6.

There is, in general, no point in adding salts to sparge water. The reactions which lower mash pH have already taken place in the mash and while it is true that additional calcium might get you some additional pH reduction in the kettle you can just add the salts to the kettle if that is what you are seeking.

If the sparge water has high alkalinity (high buffering power) then there is not enough acid in the mash to overcome it and the runoff pH will rise a lot faster than it will with DI water where there is no buffering capacity. In such cases the water is decarbonated before sparging with it and the most common method of decarbonation is simply to add acid until pH < 6. At that point there is no way runoff pH can ever exceed 6.

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Old 05-08-2011, 07:27 PM   #7
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Quote:
Originally Posted by ajdelange View Post
You are right in your surmise that if there is enough DI water the pH of the mix will be that of DI water but as I stated in my earlier post you will not have nearly enough sparge water for that to happen.

As I also stated in my earlier post, DI water has very little buffering capacity. It only takes ~0.001 mEq of acid per liter to lower the pH of DI water to 6. That's so little that the carbon dioxide in the air (0.03%) is enough to do it. There is quite a bit more acid than that in mash. Yes, eventually you can wash it all away and the pH will rise but a noted here and previously if there is enough extract remaining to measure 3 °P there is enough acid remaining to keep pH < 6.
Thanks for the reply. I read your post previously but I had been thinking (apparently incorrectly) that maybe BIAB and multiple batch sparges would approach 1:100 dilution during at least the final batch sparge before combining.

So I guess I'll add salts to the sparge that affect the flavor profile but I won't worry so much about bringing the sparge pH down.
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