Batch Sparge question.

[dixosx]

Generally I no spagre brew for my 5 gallon batches, as it works better for my system. When I do 10 gal batches I need to batch sparge do to mash tun size limitations. When I batch sparge, can I check the pH of the water after it is added to the grain or should it be done prior? Is there anything wrong with sparging this way/measuring pH this way?

I ask because I use RO water and the pH reading of the water can vary(it never reads 7), so I do not really know how much acid to add. When I add the water to the grain it seems to correct and read the proper pH.

I have had a lot of issues with tannin extraction, even with RO water. I want to make sure I do not have that issue in my 10 gallon batches.

 

[mabrungard]

Quality RO water should have very low alkalinity and tannin extraction should not be an issue as long as your water temperatures are less than about 170F. More than likely, the batch sparging water should not need to be acidified since it already has low alkalinity. The original mashing water might need a little acidification depending upon the mash grist. Bru'n Water should work for either of the methods you use. In the case of the no-sparge, enter zero for the sparing water volume and enter the full amount for the mash. For the batch sparging, you will enter the 2 water amounts as mashing and sparging amounts.

 

[dixosx]

I use Bru N Water, and it works great. I do still get tannin extraction from Distilled/RO water. Not nearly as much as my house water, but still do.

If the heated sparge water is added to the mashtun after the first runnings could I take a pH reading? If I can, should I try to keep the pH in a certain range for the batch sparge. I measure my mash pH and keep it in the 5.0 range at mash temp. I imagine that would be too low for the sparge, but would 5.5 be a good number, or is anything under 6 good.

Or... Should I just add a certain amount of phosphoric acid to my sparge water and call it good.

Thanks a lot for your response, hope these questions are not too stupid.

 

[mabrungard]

A typical low alkalinity water like RO will naturally have its pH fall into the 5 to 6.5 range when its in contact with air. But it doesn't hurt to force the pH to under 6 for brewing use.

You can take that pH reading after the batch sparing addition. Since the alkalinity is so low, I would expect that the pH of the diluted wort is still going to be well under 6 since the malt's buffer chemistry is strong and the water should not be pushing the pH up.

If you are getting tannins with RO water, I suggest that you review the degree of sparging and the final runoff gravity. In the case of fly sparging, I prefer to stop the wort runoff at about 3 Brix. Not being a batch sparger, I don't know what oversparging looks like. I don't think that gravity can be used in that case, but I expect that you could still end up diluting the batch sparge to the point that undesirable components could be drawn out.

The other thing to review is the temperature of your wort. Are you confident that the thermometer you are using is accurate?

 

[dixosx]

I use 85% phosphoric acid to adjust the pH of the mash and sparge water. For the sparge water is there a certain amount of acid per gallon of water that can be used to bring the pH to...say 5.6 or 5.5? Or, is it better to just add the water, take a reading and adjust from there to the desired pH?

 

[mabrungard]

The Sparge Acidification page in Bru'n Water is a tool that enables you to estimate the acid addition needed to bring a water of known starting pH and alkalinity to a desired pH and alkalinity. With RO water, its going to be a very small acid addition.