5-6 Gallon batches in a 5 Gallon MLT

I am new to brewing but with the help of my brew club I switched to All Grain after my first batch. I have done 7 batches now and am generally pleased with my results. I am confused on one topic though:

I have a 5 gallon Igloo Cylinder MLT and I regularly use it to make 5-6 gallon batches. I have read on these forums that this does not work well and that you cannot get OG's higher than 1.055 or so. I understand that I can only fit so much grain and water in a 5 gallon container, but I made the AHA Big Brew "Positively Porter" and hit over 1.070 OG on a 5.5 gallon batch.I think there were over 13 lbs of grain in that recipe. I do this by batch sparging multiple times until I hit my pre boil volume. The beer turned out excellent.

I know that it would be best for me to move up to a 10 Gallon MLT, but could someone point out what is wrong with what I am doing now?

http://www.rackers.org/calcs.shtml

Scroll down to the "Can I mash it" calculator. I wouldn't go much under 1qt/lbs, but according to the calculator you could mash close to 15lbs of grain. Even with modest efficiency, that'd give you about 1.080 OG.

As long as your batch sparges don't drop below 1.010 what you're doing should be fine. Below 1.010 and the risk of extracting off-flavors increases.

I've been using my 5 gallon cooler for 5 years now, with no problems. And most of my beers are between 1.070 and 1.080. On the rare times I want to brew a larger beer, I usually just borrow a larger mash tun from one of my brewer brothers I've met through here.

I just converted a spare 60-qt cooler for batch sparging "big" beers with the same fears you had, but after my last brew day, I'm pretty happy with my efficiency from my 5-gal Igloo. I fit 13lbs in there with room to spare.

I got 88% efficiency that day. Fly sparged, and hit my temps perfectly. If I could match that same efficiency (probably not), from 14lbs of grain, that'd give me a 1.099 beer, and I don't plan on making anything bigger than that.

That was the highest efficiency I've ever gotten by the way. Temps are everything.

_JP_ said:

That was the highest efficiency I've ever gotten by the way. Temps are everything.

Click to expand...

That's fantastic. But temps are just temps, right? You're going to get full conversion anywhere between 148 and 158 as long as you mash long enough. So i'm not sure that hitting temps exactly contributed to high efficiency. But it probably made an awesome beer.

jaginger said:

That's fantastic. But temps are just temps, right? You're going to get full conversion anywhere between 148 and 158 as long as you mash long enough. So i'm not sure that hitting temps exactly contributed to high efficiency. But it probably made an awesome beer.

Click to expand...

yes, you're right about the 148-158 range.

I've read numerous posts here lately where folks are shooting for 148, and their thermometer reads 10 deg high, so their efficiency plummets because they mashed at 138 (or visa-versa they mashed way too hot with a low reading thermometer). Either way, I just wanted to call attention that an accurate thermometer's necessary, along with stirring every once in a while to make sure things are evened out in there.

As for the "awesome beer".... It's still in the primary (2.5 weeks now) and just got down to 1.024. Still a little high, but that's close to the attenuation of the yeast (US-05), especially since I mashed on the high side (154). Probably keg it this weekend and call it done.

My 5 gal round has been awesome as a 1st mash tun. 30+ brews in 2 years so far and mine was used when I was given it. The most I've done is 14# of grain at .9qts/lb ratio. I'll be getting a 10 gal soon though. Not to make bigger beers, just bigger batches!

The only thing I see you doing wrong is... Rubbermaid > Igloo