Originally Posted by lurker18
Are American cornie kegs REALLY 5 gallons. The ones that I have are not, they are 4 point something, but closer to 4 than 5. I was wondering if this is due to the Imperial/American gallon difference.
I've never used a corny keg, but I did work at a truck stop pumping diesel for most of high school. A problem that frequently came up was People doing rough conversions. A US gallon is 3.7854 Liters. Most people run it quickly with it being 4L.
My gramps got on me about this when i started brewing. Here is his email to me regarding conversions
"Once upon a time the Brits established their system of weights and measures (which they modestly called the Imperial System) and spread it throughout their colonial world which at the time included us and the yanks. The system decreed that a small unit called a fluid ounce would be the basis of the volumetric system, with extensions such as:
10 ounces would be called a cup
two cups (20 oz.) would be called a pint
two pints (40 oz. ) would be called a quart
four quarts160 oz.) would be called a gallon
This was fine until the Americans decided to jump ship and set up their own system (probably a statement of contempt for the monarchy) with the cup being only 8 instead of 10 oz. All the others would stay the same in relation to this new cup, therefore:
two cups would still be called a pint, although now only 16 oz.
two pints would still be called a quart, although now only 32 oz.
four quarts would still be called a gallon, although now only 128 oz.
So that's it. That's why you MUST know whose system you are working with or you can be in deep trouble.
- Somewhere along the way the Brits decided to also go with an 8 oz. cup but not to change the others. Today's British recipes are therefore the same as American ones, but only at the cup level.
-The Imperial system is the only one ever used in Canada until we went metric.
-The Imperial and U.S,. fluid ounces are NOT exactly the same, although close enough that it's not a problem in low-tech applications.
1 U.S. fl. oz. = 29.56 ml.
1 Imperial fl. oz. = 28.4 ml.
- Beware old English cook books."
So we can actually have smaller ounces imperially, but more of them to make a gallon. Difference is about 20% which in a 5imp gal batch = 6 US gal.