Estimating Sparge pH

Is there a way, through a spreadsheet or otherwise, to estimate the sparge pH to keep it from going above 6 (which, I've read, is associated with tannin extraction). Can I simply take the water, measure its pH in the kettle before adding it to the MLT, and then add enough acid until it's below 6? Then, once it's below 6, heat it and add it to the MLT? Is there any way to estimate the amount of acid I need to add to get it below 6 if I don't have a pH meter?

Lastly, what is the lower bound for the sparge water pH, assuming 6 pH is at the top of the range? I.e. what sparge pH is too low?

Thanks!

DeltaRage said:

Is there a way, through a spreadsheet or otherwise, to estimate the sparge pH to keep it from going above 6 (which, I've read, is associated with tannin extraction).

Click to expand...

No, not practically speaking.

DeltaRage said:

Can I simply take the water, measure its pH in the kettle before adding it to the MLT, and then add enough acid until it's below 6? Then, once it's below 6, heat it and add it to the MLT?

Click to expand...

You can be pretty sure that diluting something with pH < 6 (mash liquid) with something with pH < 6 (sparge water) will not result in a mix with pH > 6 no matter how large the dilution factor.

Is there any way to estimate the amount of acid I need to add to get it below 6 if I don't have a pH meter?

For each 100 units of alkalinity in the water you need

0.96 mEq/L if your water pH is 6.50
1.14 mEq/L if your water pH is 6.75
1.25 mEq/L if your water pH is 7.00
1.31 mEq/L if your water pH is 7.25
1.35 mEq/L if your water pH is 7.50
1.38 mEq/L if your water pH is 8.00
1.41 mEq/L if your water pH is 9.00
1.46 mEq/L if your water pH is 9.50
1.50 mEq/L if your water pH is 9.75
1.55 mEq/L if your water pH is 10.00

DeltaRage said:

Lastly, what is the lower bound for the sparge water pH, assuming 6 pH is at the top of the range? I.e. what sparge pH is too low?

Click to expand...

I'd say < 5.4

DeltaRage said:

Is there a way, through a spreadsheet or otherwise, to estimate the sparge pH to keep it from going above 6 (which, I've read, is associated with tannin extraction).

Click to expand...

I think it may be possible in a more controlled and static system like batch sparging but for fly sparging I agree with A.J.

Kai

My tap water pH is 8.1 and I mix it with an equal amount of RO water. What would the pH of my sparge water be? If its too high, how many mls of 88% lactic acid per gallon of sparge water should I add?

The pH would be 7.81.

The amount of acid required would depend on the alkalinity of the water, the pH you wish to bring it to and, to a lesser extent, the pH you are starting from. There are some curves at http://wetnewf.org/pdfs/alkalinity-reduction-with.html which will help you solve this problem. In reducing the pH to 6 from pH 8.1 you will neutralize 69% of the alkalinity. If you reduce the pH to 5.5 you from 8.1 you neutralize 86% of it. The amount of acid required is the amount of alkalinity neutralized. The first step is to convert alkalinity to equivalence by dividing by 50. Thus if your alkalinity is 100 ppm as CaCO3 it is 2.00 mEq/L. 69% of that is 1.38 mEq/L so you'd need 1.38 mEq of acid for each liter of water treated. Lactic acid is a strong acid at these pH's so each mol provides 1 equivalent of acidity. The molecular weight of lactic acid is 90.08 milligrams per millimole so it will take 90.08/0.88 = 102.4 mg (0.1024) of 88% lactic acid solution to produce 1 mEq or acidity. 88% lactic acid has 1.206 grams/mL so you will need 0.1204/1.206 = 0.1 mL for each mEq. That should be easy to remember.

In your example you need 1.38 mEq/L so that for 5 gal (18.9L) the requirement would be 26 mEq and thus 2.6 mL.

For reduction to pH 5.5 you must neutralize 86% of the alkalinity or 1.72 mEq/L assuming alkalinity of 100 (2 mEq/L). For 18.9L that's 32.5 mEq or 3.25 mL of 88% lactic.

ajdelange said:

The pH would be 7.81.

Click to expand...

Doesn't this also depend on the CO2 content of the RO water, which is unknown?

Kai

You would certainly think so but at this point something is looking funny in my spread sheet. Stay tuned.

I'm going to piggy back on this thread, since it poses a similar question. I mixed up my volumes and my sparge water got too much lactic. What would be the result of a low sparge pH? Say 5.0-5.1?