Missed my og for the first time, need guidance

Hello I just moved from 2.75 gallon batches to 5.5 gallon batches. With the 2.75 gallon batches I was always getting 2-4 points higher og than what the recipe said I would get which i thought was awesome. But today I did my first 5.5 gallon batch, which was a leffe clone by the way, and I ended up 6 points shy of my og. It was supposed to be 1.067 and I ended up with 1.061. I'm trying to figure out why I came out low so I thought I would ask the pros on here. Heres what I did different on this brew as compared to my last good brew:

1. moved from 2.75 gallon batches to 5.5
2. moved from a 5 gallon brew pot to a 10 gallon pot
3. used a immersion chiller for the first time (which was awesome)

Thanks all that I can think of that is different from my past brews to this one.
This brew did come out about a .50/.75qaurt above my 5.5 gallon mark but I don't believe that would account for being off by 6 gravity points would it?

BTW, I did nail my mash temp. at 152, so I know that didn't cause my problem

Thanks for any info on why I missed my target OG

Is this an all-grain or partial mash brew?

And being off by a half a quart might not account for the total difference, but the sample you pulled with a higher total volume may not have been totally uniform so it could have been slightly off. Honestly, 6 points off, with slightly higher than expected volume, plus other variables involved, I don't think you have anything to worry about.

It was a allgrain brew, also I was a little shy of my 5.5 gallons and then added too much top up water which put me over 5.5. That top up water maybe wasn't mixed in good enough with the wort? Could that have threw me off?

JBrady said:

It was a allgrain brew, also I was a little shy of my 5.5 gallons and then added too much top up water which put me over 5.5. That top up water maybe wasn't mixed in good enough with the wort? Could that have threw me off?

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Yep, adding top off water is a usual suspect when getting inaccurate gravity samples.

Since it was an all grain brew, were you taking samples elsewhere in the process, or only after the boil was done? If that was the only sample you took, without knowing your gravity going into the kettle before boiling and then subsequently adding top off water it's nearly impossible to say where the error may lie.

yes I only checked my gravity post boil, I actually always grab the sample before i put the wort in the fermenter, I forgot this time and had to pour it back out of the carboy after already diluting it with top up water. I guess I'll leave my 75% efficiency alone for now and see how my next brew day goes on friday

I had the same thing happen with my first AG last Saturday. I didn't know how much boiloff I'd get, and, in the end, I had to top off with almost a full gallon of water. I ended up about 10 points off on my OG. I'm sure my efficiency wasn't that great, but some suggested that my topoff water may have been the culprit, too.

I still had great fermentation, and the beer smells great, so I'm not too worried. Like you, I'm just going to be a little more detailed in my process next time.

yea i have no doubt that mine will taste great, it'll just be a little weaker on the alcohol. Fermentation is grinding away, I already had to swap from a airlock to a blow off rig.