I brewed a honey wheat extract kit today. In order to guarantee water quality and make sure my total water adds up to 5 gallons, I purchase 5 gallon jugs of spring water from the grocery store every brew. I boiled 3 gallons of wort and then poured 2 more gallons to top it off. However, the total liquid in my fermenter I got was a little over 4 gallons. The OG was 1.045 and I was getting 1.040. I am wondering if using this 5 gallon jug water technique is a good idea because I know some of the wort will evaporate. Any suggestions? I'm wondering if it is more important to have the OG or have 5 gallons of beer?