Why can't I brew all-grain with this water?

[bracconiere]

Yes tannins cause astringency. Tannins are extracted from grain husks when you have both high temp (above ~170°F) and high pH (above ~6.0.) High temp alone will not extract tannins. If it did then all decoction mashed beers would be astringent. Sparging with too hot and too alkaline water is what gets you tannins. Acidify your sparge water to pH 5.8 or less, and it doesn't matter how hot it is.

Brew on

glad we're back on topic with OP's problem....i had a serious tannin problem, i thought it was yeasty, bought all kind of filters and stuff...i asked the local brew-pub owner about it, he told me right off the bat, "lower your sparge to 160f", solved my problem...that was before i had a ph meter, and i'd have no idea what the ph was...but i was using boiling hot water....

 

[BrewnWKopperKat]

glad we're back on topic with OP's problem

We never left that topic, just started a couple "on the side"