15 gallon batch

I currently brew 5 gallon all grain batches with the occasional extract here and there. I have a 10 gallon brew pot (can comfortably boil 9 gallons). I keep over thinking how best to end up with 15 gallons of extract for Christmas party. Easiest way would be to concentrate then top off with water right? How best to do this? I would prefer not to have to brew multiple batches. I have two 6.5 gallon carboys and two 5 gallon carboys. Dry yeast for each carboy? Won't be high gravity, plan on brewing an easy drinking Amber to please the masses. Any help/suggestions would be appreciated. Cheers

 

When I brew extracts I boil about 1/2 the final volume then top up so maybe 8 gallons to start in your 10 gallon pot then top up to 15 gallons. The top up would be the tricky part. I guess you could measure out equal amounts so that you add the same amount of top up water to each. Any yeast as long as you use the proper amount and get relatively equal in each fermenter.

Use an online recipe calculator to formulate the recipe so that you get the right concoction for the concentrate - before the top up.

 

Since you're making a less complex beer, the boil size won't have as big of an impact I don't think. I'd do a 9 gallon boil. Before the boil is over, I'd fill each carboy with 5 gallons of water and mark the side with a sharpie. Leave in/fill back up 2 gallons of water in each carboy and then syphon the wort into each carboy so it fills up to the sharpie mark. You could do the same with an 8 gallon boil, but even divination would probably be hard to achieve. And as kh said, use BeerSmith or another recipe calculator to make sure the boil size you end up going with matches with what you want.

Obviously it's backwards from topping off, but the order does't matter. I usually pour my wort onto water and then top off again to get to 5 gallons. It allows me to gauge my efficiency and boil off.

 

Ok, I guess I wasn't over thinking it. A little more complex than I thought. I will be using beer smith for the appropriate extract/hop additions. Thanks