I'm w/jeffy and BigMonk on the vigor of the boil. I was losing a lot in my initial batches (5-gal. recipes, typically 3-gal. boil) using a high-rolling boil. It occurred to me that if the wort is 212º at an easy boil, the job is getting done and I'm not losing as much volume. I check my level at the tail end of the boil and add (distilled) water to the 3-gal. mark. Not very scientific, granted. I'm thinking of buying an immersion chiller, so might have to shift to measuring the loss after a non-wort 3-gal. boil and adding that volume to my pre-boil volume since displacement would make it impossible to measure the finish. I once made the (apparent) mistake of adding water to the cooled wort in my fermentation bucket to bring it up to the 5-gal. mark. Ended up tasting thin, so I figured that was the problem.