Just water, about 5 gallons or so. Plugged it in, set the temp for about 150 and off it went. Took about 15 to 20 mins to reach temp. Then the heat element dropped down to about 20 percent and it held 150 for 60 mins, not even a degree of difference on the display. I am so fired up. This means all my stress of temp issues are pretty much gone. Figured out how to do step mashes and delay the start as well. Looked on Youtube and found a super simple way to make a whirlpool arm out of stainless steel tubing and hook it to the chiller. I am really fired up about using it. Gonna order the needed ingredients for a simple SMaSH ale I think to try out.