Can you pitch too much yeast?

Ok. My all-grain beers seem to have a mediciny flavor that can be caused by yeast or using bleach as a sanitizer. Since I use star san for sanitizing, the bleach issue is eliminated. So what else could cause it. My beers start in the 1.07-08 range and fementation starts within 24 hours and is done in a few days. I use smack packs with a starter. Can you pitch too much yeast?????

You can pitch too much yeast. That usually results in increased diacetyl, acetaldehyde and low attenuation. Pitching too much, will also cause the yeast to be less productive in your next beer.

How to Brew-Off Flavors

I had some trouble with the medicinal off flavor that you described. I found that it was caused by using tap water, even if it was run through a carbon filter, since it still contained chloramine. As soon as I made the switch to RO water, my medicinal flavor went away.

You CAN pitch too much yeast, but it isn't at all likely. You can pitch four smackpacks, and still not overpitch, for many beers!

It sounds like a water issue- chloramines in the tap water specificially. What kind of water are you using?

Could also be that your crush is too fine or you are oversparging (or both).

Maybe you can overpitch, but it's highly unlikely using smack-packs and starters, unless your starters are HUGE.

"Mediciny" can describe a diverse range of off-flavors. One that comes to my mind is phenolic (sort of a bandaid taste). I'm overly sensitive to it, and frequently taste it in home brews, pub brews, and micro brews, and the prime suspect is tannins from over-sparging.

Do you have temp control for your fermentation? I've had some bad flavors result from fermenting too high.