Howdy Canadabrew,
Now this is for boiling water.
Just fill your stove top with whatever.
You will realize the bigger ones get to boiling slower and cool slower as well.
But they boil more water.
Hmmmm...
I been brewing 15 years and I still can't figure it out.
Depends on how many burners you have, just fill em.
Now for your wort,
my old canning pot is about 2.5 gallons too.
I bought my old girlfriend a canner for her birthday 30 years ago,
and she laughed her ass off, a canner! a canner! and left it with me when she moved, so now its my brewing pot.
Now, for the wort, yes, you need a big pot.
2.5-3 gallons is good.
Imagine, some folks like a full boil.
Boiling the entire 5 gallons of wort at once,
+ rinse water in different pot.
=6.5 {minimum} gallons of water.
Or more.
But I ain't never done it that way.
On the other hand,
Boiling your wort in one gallon of water is too concentrated of a wort.
Ain't no way.
Bigger the better, but...
I am limited by a plain ole stove top...
just match your pots to whatever your heat source.
After brewing for a long time I know which '5-6' pots to use for brewing,
bottling, reracking. In fact I have back in my brewery,
{which used to be a pantry}
a equipment list nailed to the wall which specifies which equipment I need to Idophor for, 1. brewing, 2. reracking, 3. botting.
So I don't forget.
Clorine kills microbes in water, well,
think about being yeast trying to live in water with a bunch of clorine in it !
Trying to make good ale in clorinated water, no way!
I have boiled my tap water for years and just last spring,
the owner of Homebrew headquarters up in N. Dallas, old Kelly,
found out it was taking me 8 hours to brew a batch.
"8 hours and you have been doing this for 15 years!"
"Yeah well I live out in the woods but for my hounds alone,
and I have always boiled my water, the clorine you know."
Kelly says buy cheap 1 gallon, bottled water to use for your brew and rinse water too.
Use cheap bottled water.
No clorine and it costs fifty cents, a gallon.
And you'll save propane too,
living way out in the sticks as you do.
\Some folks use tap water!
And it was so, now its late and I must adjurne ya'll,
"time for a homebrew."
J. Winters Knife