totally new to all of this and I want to get it right. Im not exactly sure what to put in the boxes for the volume and weight of my mash tun. Its a common converted Spartenburg Keg. I know it holds 15.5 gallons (right?) but is that what I want to put in the volume box? I mean I'll never put 15.5 gallons in there will I? and What is the weight? What specific heat is normal for this set up.. thanxx in advance for any help! ;D