How much water will boil away?

[jonesaabc]

Hello,
I've been hanging around for awhile, but this is my first post. I have brewed four batches so far, they were all kits. I have been brewing in a four gallon ss kettle. This small kettle and the brewer's best kits call for a 2.5 gallon boil, and then add water to the fermenter for the five gallon batch. I have recently aquired a 15.5 keg to brew in and would like to know how to figure how much water boils away in a one hour boil? I would like to do a complete five gallon boil.
Thanks

 

[Nugent]

It will depend on your system, but count on 15-20% evaporation loss (that's what I get with the keggle + 65,000 BTU burner. When brewing your first batch on the bigger system, keep careful track of your starting/finishing volume and the change in your pre-boil and post-boil gravities. It will help you dial in your system and allow you to make future adjustments to things like the intensity of your boil, etc.

 

[ICanHazBeer]

I would say do a test with your current system just using water. I did this just yesterday with my new 15 gallon megapot and SQ14 burner. I lost 25% of my water over a 60 minute boil.

 

[jonesaabc]

Well, here's what I did. I started partial mash with 2.5 gallons and added 3.5 gallons to keggle for a total of six gallons. After adding ingriedents and boiling for an hour, I ended up with about a half galllon too much wort.

My OG was supposed to be in the 1.051-1.055 range and I ended up with with a starting gravity of about 1.042. I have already pitched the yeast. Can I boil and add some dme to get the OG where it is supposed to be? If so how much do I need to add?

 

[Yooper]

Well, here's what I did. I started partial mash with 2.5 gallons and added 3.5 gallons to keggle for a total of six gallons. After adding ingriedents and boiling for an hour, I ended up with about a half galllon too much wort.

My OG was supposed to be in the 1.051-1.055 range and I ended up with with a starting gravity of about 1.042. I have already pitched the yeast. Can I boil and add some dme to get the OG where it is supposed to be? If so how much do I need to add?

You could, or you can just leave it since you're only .009 low. A pound of DME would get you to where you want to be. If it were me, I'd probably not worry about it.

 

[jonesaabc]

I think I will leave it as is and adjust for the next time.