So I brewed two batches of beer last week, a brown porter extract kit, and a mini-mash beglian wit.
Everything went well with the brown porter, and the hydrometer reading before I put it into the fermenter was 1.058. I realized that it wasn't quite 5 gallons, so I added about half a gallon of water to the fermenter and took another gravity reading. This time it was 1.052. I wasn't really thrilled about losing that 6 gravity points, but the kit said the expected gravity was 1.048-1.052 so I was at the top of the range and still pretty satisfied with the outcome.
The witbier was a somewhat the same situation, but since it was my first mini-mash, I'm not really sure if I messed up somewhere along the way. First, obviously, I mashed the grain. At this point I had used about 3.25 gallons of water for the mash/sparge, but when it was trasferred into the kettle it was around 2.5 gallons. I am not sure if that is normal. I added water to the kettle and proceeded with the brew as normal. At the end of the brew it was basically the same thing, I ended up with less than 5 gallons, and added water (about .5-.75 gal.) to the fermenter to top it off. This dropped my gravity to the same 1.052, but the range of the kit was supposed to be 1.060-1.064.
I didn't take a gravity reading before I added the water the second time, but I'm sure I was right about par with the kits expectations. So my question is this: Should I be adding water to the beer to get the 5 gallons that I am supposed to produce, or am I just watering down a good porter that exceeded expectations, and a witbier that would've hit the target gravity right around perfect?
Thanks for any help/suggestions you guys can give.
You "should" do whatever you want.
Yes, you're "watering down" your wort. You're thinning the wort, dropping the gravity, and likely cutting into body of the finished beer. This is all fine, and adding water into the fermenter is pretty standard for the reasons you've given (dropping gravity and/or increasing volume). It isn't really a good or bad thing. Personally, I'd rather have 4.5 gallons of 1.058 porter than 5 gallons of 1.052, but that's just me. If you want five gallons, add the water. Either way the beer will probably be fine. But I wouldn't do it.
Your missing .75 gallons in the mini-mash was probably absorbed by the grain.