I have never used a hydrometer (gasp!). I simply have no use for it. It’s a lot of work for a little payoff, in my humble opinion. How do I know how much alcohol is in my beer? I drink it. That’s one way. Another way is little more scientific: I enter my recipe into free brewing software (brewtoad.com), which tells me the ABV. Sure, it might be off .1, .2 or.3 percent – there are several factors at play – but who cares? Relax, have a homebrew, says Charlie. If you make sure your process is right – mash temp, aerate, fermentation temp – the ABV will turn out just fine. It’s not rocket science. The Egyptians were brewing, for God’s sake! If the conditions are right, it will do it’s thing.
Brewers take “gravity readings” with a hydrometer before, during and after fermentation to make sure the beer is fermenting properly, and that the beer is in fact done fermenting. That’s several ounces of wasted beer, time, effort, and possible infection; but the concept is very important. If the beer is not done fermenting, and you bottle it, then you could have exploding bottles, or over-carbonated beer. Both suck. In full disclosure, I have had one or two over-carbed batches. However, I think those were rookie mistakes. I fermented one in my cold basement, and the other I simply bottled too soon (it wasn’t done fermenting…okay, yes, I realize that a hydrometer would have helped. You got me :).
The real solution is to create the conditions for a good fermentation, to make sure the temperature is around 70 degrees, to make sure you aerate the wort before pitching the yeast, and to watch your airlock activity. Also, my system has a spigot on the fermenter, so I can taste the beer whenever I want. I can tell if a beer is too sweet. I did this a few days about with a DIPA. After 6 days of fermenting, and a few days of no airlock activity, it tasted nice, dry, and bitter. It was done; ready to dry hop. One Pot Brewing could easily accommodate a hydrometer (in fact, I have one. It was given to me as a gift. I tried to use it once).
If you want to use a hydrometer, by all means you should. It will give you a more accurate picture of your beer, how efficient your mashing was, and all that good stuff. I’m just saying you don’t need one.