I have a leftover gallon of topoff water... what gives?

[LSDracula]

the last 2 beers I brewed I ended using 5 gallons of water and part of a sixth to end up with 5 gallons in the brew pail
today I only ended up using 5 gallons exactly

there are 2 differences between this batch and the last 2 they are

#1 an extra pound of DME and about a pound of extra steeping grains compared to the last 2 recipes

#2 I did a 3 gallon boil instead of 2

did the extra pound of DME actually fill up that much extra volume or
did my gas stove just not get hot enough to have a vigorous enough boil to get the same rate of evaporation as I got before
I am confused

BTW the final gravity was right on brew calculus predicted O.G. of 1.070 it ended up being 1.074

 

[Thumper]

the last 2 beers I brewed I ended using 5 gallons of water and part of a sixth to end up with 5 gallons in the brew pail
today I only ended up using 5 gallons exactly

there are 2 differences between this batch and the last 2 they are

#1 an extra pound of DME and about a pound of extra steeping grains compared to the last 2 recipes

#2 I did a 3 gallon boil instead of 2

did the extra pound of DME actually fill up that much extra volume or
did my gas stove just not get hot enough to have a vigorous enough boil to get the same rate of evaporation as I got before
I am confused

BTW the final gravity was right on brew calculus predicted O.G. of 1.070 it ended up being 1.074

I am too much of a newb to know for sure, but I am betting on not a enough of a vigorous boil.

New we let the experts chime in an set us straight.

Cheers,

 

[newbeerpig]

My guess is number two is the cause, if you used the same diameter pot but more volume you may have found your stove couldn't boil as vigorously as before and therefore your boil off is not as much. Using more grains should have actually reduced your remaining volume, I figure about a quart of loss for every pound of grain used unless you squeeze your grain when you are done which is not the best idea. The Malt will add some volume but I think it would be offset by the extra grain. There also may be other temperature conditions going on that may have accelerated the evaporation before, you also may have had different amounts due to different volumes of trub and other conditions. I rarely end with the exact same amounts when I am brewing I just know I will be close and plan accordingly. As long as your numbers hit you did well and just have the waiting game ahead.

 

[LSDracula]

My guess is number two is the cause, if you used the same diameter pot but more volume you may have found your stove couldn't boil as vigorously as before and therefore your boil off is not as much. Using more grains should have actually reduced your remaining volume, I figure about a quart of loss for every pound of grain used unless you squeeze your grain when you are done which is not the best idea. The Malt will add some volume but I think it would be offset by the extra grain. There also may be other temperature conditions going on that may have accelerated the evaporation before, you also may have had different amounts due to different volumes of trub and other conditions. I rarely end with the exact same amounts when I am brewing I just know I will be close and plan accordingly. As long as your numbers hit you did well and just have the waiting game ahead.

Thanks for the info!
Also I had some foam in my fermentor so my final volume may not have been exactly 5 gal.
Worst case scenario I didn't put enough water in, but I can always add a little extra water with priming solution at bottling time.
I guess I shouldn't worry my beer started showing signs of fermentation already today. After only 2 hours! I am now a believer in the power of a yeast starter!