Brewed over the weekend, a kit from Austin Home Brew and the recipe said the expected post boil gravity should be 1.057. Mine came out to 1.051. My efficiency was 75% (it was 78% the last time... so pretty consistent). I ended up sparging 2 quarts more than I needed for my 6.5 gallon pre-boil volume, but wouldn't think it would make that big of a difference. Everything I have read said that the kits assume 75% efficiency. My first brew day from an extract kit had the gravity almost exact, so I don't think it is my hydrometer. Any clues or a starting place to look for my lower than expected gravity? Water maybe?