I have a situation where I switched from bottled spring water to tap water filtered through the 10" carbon filter, found online, and my beer's attenuation has suffered, seemingly, because of the change. My attenuation levels for identical recipes went from 1.013 - 1.015 to 1.018-1.019.

Increasing the amount of aeration and/or oxygenation at the start has no effect on the FG. Is there maybe a third cause I am overlooking, or can filtering water through a carbon filter change the water chemistry enough to alter the amount yeast attenuates the wort.

- Dave

RESPONSE:

Water composition has a great effect on the mashing characteristics of wort and the fermentation characteristics of the yeast. Calcium and magnesium are the two key minerals. The water should contain 50-100 mg. of Ca+++/liter and 10-15mg. Mg+++/liter. Your tap water may be softer than the spring water. I would try adding 1/6 tsp. of gypsum and about half that amount of Epsom salts per gallon of water to be used for mashing.

The calcium is needed to protect the starch conversion enzymes in the malted barley. Magnesium is needed in the yeast metabolic process. Let me know if it works.

Dr. Clayton Cone