I have been getting a slight but distinct tannin flavor in my beers and I can't seem to find the cause. I'll try to explain my process in detail. I use all RO water even though my well water has moderate alkalinity (total alkalinity: 57) and no other issues (Ward Labs test). I use RO because I already have an RO unit and it is convenient to use, so that brings the alkalinity down to probably well below 5. Do I need more alkaliniity? I add calcium chloride and gypsum to get about 75 ppm Ca. I get the same tannic flavor in all kinds of beers (Pale Ale, Helles, etc.) with both pilsner and pale 2-row base malts. I do only a single rest. Should I try a protien rest? My mash pH is always arround 5.2-5.3. If anything this is on the low side. Could low pH cause tannins? I thought only high pH was an issue. I adjusted my barley crusher to slightly below the factory setting. Not sure the gap off-hand but I don't have any problems with stuck sparges. I batch sparge with all RO water and no water treatment. Could that be an issue? I didn't think I needed acid since it is RO. I vorlof a quart or two then let it run into the kettle. I get great cold break which is pretty much all left behind in the kettle and chill down below fermentation temperature. I'm at a loss for what to do next. Any suggestions?