Can Hot Tap Water Effect pH?

[sabitu]

For some reason with my last brew my mash pH came in high at 5.7. I used Bru'n Water to calculate my salt additions to get my pH to 5.4 beforehand. I dilute with 80% distilled water and use tap water for the rest.

I have used Bru'n Water before to accurately predict my mash pH. The only thing I did differently this time is that I used hot tap water instead of cold. I was wondering if this could account for my pH coming in .3 too high? The water amounts were 7.5 gallons distilled and 1.9 gallons tap water. I do a full volume BIAB mash.

 

[ajdelange]

With a typical mash that would require that the tap water have an alkalinity of about 1000 so no, it isn't likely. More likely you mis-entered something into the spreadsheet. The spreadsheets can make errors in pH prediction of as much as 0.3 but usually they are better than that.

 

[sabitu]

Here is all the data from Bru'n Water that I used for this brew session. I didn't see any mistakes but maybe I'm missing something. My pH meter was calibrated before use so I don't think that's the problem.

 

[ajdelange]

I can't really tell much from the spreadsheet but we can look at what's reasonable. I don't know a thing about Fawcett Pearl except that it is a base malt. I don't know a thing about Carastan except that its color is apparently 17 L and that it, therefore, presumably has properties something like other malts of similar color and that whatever the differences are they don't much matter as it is only 5 percent of the grist. Same for white wheat. Thus what happens will be determined mostly by the base malt. Most base malts have a DI mash pH between 5.6 and 5.7 and that is, therefore, where you would expect the mash pH to be with distilled water. Using Crisp Maris Otter as a representative base malt the DI mash pH would be 5.69 without any other malts and typical specialties in the quantities given might pull that down 0.01 pH.

Taking the blended water chemistry listed as written we note that the high calcium level might pull mash pH down 0.11 and the magnesium 0.02 whilst the reported alkalinity would offset about 0.06 of those decreases for a net estimated pH of 5.61. Thus 5.7 isn't an unreasonable estimate for the pH of the mash with 20% tap water, be it hot or cold. OTOH 5.4 isn't really a reasonable estimate for the mash pH even with all distilled water or all distilled water keeping the calcium and magnesium but eliminating the alkalinity and I don't need a spreadsheet to tell me that.

I can't really tell why you get an estimate of 5.4 as the spreadsheet is locked to keep guys like me from being able to see how it works. I can see, from what it displays, that the water is given an acidity of 1.5 mEq/L when in fact its effective acidity is more like 0.5 mEq/L. This suggests an extra mEq/L acidity which would explain an estimated mash pH of 5.4 but I don't see any acidity addition anywhere in what you posted. Perhaps I just missed it. At the same time I see total mash acidity listed as 0.5 when, in fact, the acidity of the mash wrt pH 5.4 is more like 1.4 mEq/L. But then although I do know what acidity is I don't know that it means the same thing here.

Stepping back for a minute we an see that a mash like this is going to have buffering of 30 - 50 mEq/kg•pH and that means to get a swing of pH of ∆pH = 0.3 with 6.8 kg malt you are going to need 0.3*6.8*30 = 61mEq to 0.3*6.8*50 = 102 mEq of alkalinity or acidity. And, as what you observed came only from changing the source of 7 L of water we have to conclude that the change in that water was 61/7 =8.7 to 102/7 = 14.6 mEq/L. That's just not reasonable. At this point the possibilities are
1)Bru'n Water does a terrible job of modeling Fawcett Pearl
2)Fawcet Pearl isn't anything like an ordinary base malt
3)You made an error in your pH reading.
4)Something else I haven't thought of.

 

[sabitu]

This is the first time I have used Fawcett Pearl malt so maybe that's the culprit. Next time I brew this recipe I'll see if I can pinpoint where the rise in pH is occurring. Thanks for the info.