Dilution Techniques Question

[Brewvy]

I've brewed an American Lager with plans of finishing with 12.5 gallon of 1.054 sg wort to ferment in my sanke keg.My actual starting gravity is 1.062. I am thinking of adding a gallon of distilled water to the fermenter to achieve 13.5 gallons. Will two gallons of head space in my keg be enough for the kreusen, or will I just blow off a bunch of beer? I would prefer to dilute post fermentation.Assuming I add 10 percent distilled water post fermentation , would that in turn take 10% off the original gravity (1.062-0.0062=1.056) at least approximatly? Could I just boil the priming sugar(yes I'll be bottling all 14 gallons) in the entire gallon or so. I want a light summer drinkin' beer ,not another strong ale that I always seem to make.

 

[devilishprune]

To get your target gravity, you would need a total volume of 13.8 gallons. I would just boil the 1.3 gallons of water with the priming sugar and add it all at the same time.