Diagnose off flavor

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Oct 20, 2008
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The last few times I've brewed a stout I've gotten what I believe is a metallic/astringent off flavor. I believe I know what's causing it but I would love to get input.

My process:
2 keggles, copper immersion cooler, silicone tubing, chugger pump, glass carboy
Tap water + a crushed camden tablet in preparation for strike.
I crush my grain pretty fine because I do a batch sparge and wanted to up the efficiency a bit. This last run I got about 75% - 80% efficiency.

I heat my water in the bk/hlt until I hit the appropriate temp. I transfer the water to my mlt and mix it all up. This last batch I hit 156 F. It's an insulated keggle so it holds temps but I usually start to recirculate the wort through the copper immersion chiller 20 - 30 minutes in. I keep the bk at around 180 degrees and start recirculation when the mash temps drop a few degrees. Once the mash is at the appropriate temp I stop recirculation. I mash for an hour total.

After the mash I transfer the rest of the water from my bk/hlt to the mlt. Last time I hit about 165 F. I then recirculate the mash into itself (not through anything) to settle the grain bed. After 10 minutes of that I transfer to the bk for boil. I don't have a pH meter so I haven't checked my mash pH or my water pH.

After boil I cool with the immersion chiller and I can usually get it down to 100 degrees in 5 minutes and 80 degrees in 15 minutes. I'll put the carboy in my fermentation chamber (68 F) until the wort is ~75 F. I pitch a yeast starter I prepared and wait 4 days before trying it. At this point there is the off-flavor.

I clean my equipment with either barkeepers friend or PBW and sanitize with star san.

Any ideas? At this point I'm close to sending my water in for testing or just purchasing spring water from now on. I might even pick up a pH meter.