Why 5-gal. batches?

[brewwitch]

Hi

Every recipe I have encountered is for a 5 gallon batch.
Is there a reason for this? I mean can one easily 1/2 the recipe?
If so, are there any special considerations like changing time required for
fermentation or anything else?

thanks!

[zoom6zoom]

Probably because the most readily available carboys are 5 gal, as are the soda kegs that many of us use.

You could cut the recipe in half, but the labor involved remains the same, so why bother?

Fermentation time would not change.

[beerking]

There are probably several reasons for 5 gal batches, most of which all boil down to one general reason: convenience. 5 gal is about the most you would want to lift in a glass container, most plastic fermenting pails run 5-7 gal in size (you need extra head space for the foam during ferment), and the glass carboys many use come in 5 and 6.5 gal sizes.
Once you go to all-grain, many choose to brew bigger batches, 10 and 15 gal being most common. The reason there is time. It takes the same amount of time to brew 10 or15 gal as it does 5 gal, and with all-grain brewing you are looking at a significant time investment.
Brewing a half batch (2-3 gal) can be done, but in racking and transferring you will frequently lose ~.5 gal. From a 2.5 gal batch, that means 20%! That is a lot of beer to lose!
Fermentation time, boil time, etc, would all be the same, so you go back to the issue of making the most of your time investment.
I have occasionally made half batches as kind of "test beers." You could use only one can of a new extract to see how it is, or with all-grain you could try a new grain or techniques without worrying about ruining too much beer if it does not work out.

[brewwitch]

Thanks a lot. Question answered. I was more concerned about ruining all that beer since I am inexperienced.

thanks again!