Most of my beers where I live now have been astringent (5 or so). Some more some less. I found one of the culprits after lots of research: I have incredibly high alkalinity (400ppm CaCO3). So I have decided to mix my own water with destilled water and the usual salts. Now I am worried about oversparging. Presuming I construct ideal water and calculate my mash and sparge water using the usual method, do I still need to worry about oversparging? If so how do I go about avoiding this on the grainfather? I've never read a detailed technique anyway. Keep sampling the sparge runoff every 5 mins and test the pH using a meter?

1 Answer 1


Sparging efficiency is, generally speaking, not a factor of water chemistry. By changing your high alkalinity tapwater to distilled water with added salts you should see no difference in sparging efficiency, and the same sparging volume as you used before should work fine without introducing a risk of oversparging.

Using a pH meter on your runoff is also not very useful; it won't tell you anything about when to stop sparging. The tool of choice to determine that is a hydrometer or refractometer. (The latter is easier to use because cooling down a drop of green wort to the instrument's calibration temperature is much quicker than cooling a tube full of wort.) Test your wort gravity regularly during the sparging process; for an average strength beer you don't want to go below 1.008 in order to prevent oversparging.

  • Thanks for the answer! I wasn't very precise: I know that oversparging has nothing to do with water chemistry. I don't do batches that often and am keen not fix one problem but still have another. All of the strike and sparge water calculations I've seen are just related to vessel volume, grain absorption etc. I've never seen any kind of calculation or formula relating to oversparging. Is there no rule if thumb or is measuring the only way? Refractometer might be easier that hydrometer, but it will still be a pain to get samples with the grainfather.
    – dashambles
    Mar 18, 2019 at 23:22
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    Actually pH does rise as you sparge, and it's increased pH which causes an increased risk of tannin extraction. this point is about pH5.8. One way to decrease this risk is to acidify the sparge liquor down to about the same pH as the mash. The issue here is also not with sparge efficiency, which is only tangentially related to oversparging.
    – Frazbro
    Apr 8, 2019 at 22:49

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