Adding water to Boil?

I am not able to do a full boil yet and I am limited to 2.5gal because of my pot size. I am losing a gallon during a 60 min boil leaving me with a very concentrated wort before adding water in the primary. Is it advisable to attempt to add water during the boil to make up for what steams off?

There is nothing wrong with a concentrated wort after boiling. It will affect your hops utilization some, but your utilization is already affected due to the partial boil. If you want to add additional water to the boil it will not hurt anything you are doing. What I would recommend is using a small pot with water which should come to a boil more quickly, and pour that boiling water into your brewpot. I would not advise pouring water that has not been heated to at least very near boil, as it could stall your boiling wort.

+1 to that. Make sure that you have it already boiling. We added water that was not boiling to ours once and the boil was twice as long.