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Author Topic: RO water pH  (Read 4446 times)

Offline hike20

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RO water pH
« on: September 25, 2010, 11:31:33 am »
I'm trying to learn about water adjustments and have been following the great discussions on the topic here. I only have pH strips for testing at the moment, one strip goes from 4.6 to 6.2, another that goes from 4 to 8. I'm using the new 2.0 version of the EZ Water Calc spreadsheet to estimate my mash pH, making adjustments and using the strips to see if I'm in the ball park.

So today using the strips my mash was reading around 5.0. I was surprised that it came out so low. So I decided to test my source water. For this batch (2.5 gallon btch) I mashed with 2 gallons of water, with 6 quarts of that being RO water that I bought at the local grocery store, the rest from my well. Since my mash was so low I tested the RO water with the strips and in came in around 5.0 too! The well water was around 7.

Does that make any sense? Is it normal or likely for RO water to be that acidic? If it is, then should I try to compensate for that in my mash pH calculations? Here's all the gritty details:

4# Marris Otter
4 oz Aromatic
4 oz Caramel 120L
2 oz Special Roast

Well water, from Ward Labs:
pH 7.5
TDS 413
Cations/Anions me/L 8.0/7.5

Na 6
K <1
Ca 90
Mg 39
Total Hardness 388
SO4-S 13
Cl 13
CO3 <1
HCO3 355
Total Alkalinity 291

I don't have a water report for the RO water, but I assume it's pretty close to 0 on everything. I know, I shouldn't assume.


Offline thcipriani

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Re: RO water pH
« Reply #1 on: September 25, 2010, 01:30:15 pm »
It is atypical for a mash pH to come in that low using distilled water and that malt bill.

While it's not impossible for the mash pH to be that low using that grain bill it is improbable.

First, the pH of RO water is a) unimportant to brewing by-and-large and b) is often lower than what people typically quote (7) since CO2 from the atmosphere will dissolve into RO water.

Second, I don't believe the pH strips you are using are adequate to test the pH of your mash. the pH 4-8 strips are strips with which I am unfamiliar, but the 4.6 - to 6.2 strips are likely the precision labs pH 4662 strips that my LHBS sells.

The reasons I believe these strips to be inadequate for mash testing are
a) Your strips are of unknown accuracy - the EMD strips have shown that they have an error that causes them to read 0.3 pH units lower than the actual pH of the solution - the precision labs strips (which are much cheaper than EMD colorpHast strips, if we're using price as a quality determinate) may very well have an error of which you are unaware. Furthermore, the color index on the Precision Labs would indicate that the accuracy of these strips is +-4 which is not adequate for any brewing application, IMO.
b) The gradation of color on the precision labs is not adequate for one to draw any strong conclusions. A color gradation of yellow to brown is not a range in which definitive conclusions could be drawn. Viewing a strip under a tungsten bulb vs a florescent bulb could very well make the difference of .8 of a pH unit.
c) I've actually had the Precision Labs strips change colors in their sealed container, and not to a color that would indicate that there was excess moisture in their container, rather a color that would indicate the strips had dried out. The strips start as a very vibrant yellow and when I looked at the container after having purchased the strips 6 months prior the strips color pad (for lack of a better term) was a very pale almost white.

Having said all that, I think the best course of action for your water when brewing pale beer would be to cut it down with some RO - just like you're doing and add back some calcium in whatever way you see fit. When you don't have a pH meter it is difficult to get your mash pH in the right range because you don't know when you're there. My only recommendation is to NOT add additional alkalinity (like chalk, baking soda or calcium hydroxide) to your water until you have an accurate means of measuring pH. Your mash pH is more likely to be too high than too low.
« Last Edit: September 25, 2010, 01:40:14 pm by thcipriani »
Tyler Cipriani
Longmont, CO

Offline hike20

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Re: RO water pH
« Reply #2 on: September 26, 2010, 08:44:24 am »
Thanks Tyler. The strips are indeed the 4662 variety. I guess I'll just trust in the estimations from the spreadsheets for now. Here's what I added to the mash based on the data from Kai:

0.6 gm CaCO3
0.8 gm Gypsum
0.8 ml Lactic Acid 88%

I tested the mash pH with the strips before adding the acid. My intent was to add more or less acid to dial it in if needed. Since I had serious doubts about the strips at that point I went ahead and added the acid and hoped I' be close.

I tested the conversion with iodine at 30 minutes. The mash wasn't fully converted yet, so I let it go to 60 and retested. It appeared to have completely converted at that point, so I figured I had something that would make beer. I hit my pre-boil and post boil gravities so I felt pretty good about it.