I am getting ready to brew my first 5 gallon batch with my Herms system. once I figure out the water to grain ratio how much heated water do I put in the mash tun to start? My HLT will heat the Herms coil and my boil kettle will serve to heat all the mash/sparge water. I just need to understand how much water to start off with in the mash tun so I can add the grains and then slowly fill the mash tun with water from my boil kettle? Thanks.