I don't have the notebook with the numbers handy, but I ran last winter using tap water in the kitchen. I kept a cooking thermometer in the outlet flow, and frequently checked the temp by hand or point-and-click IR thermometer on the outside of the condenser. Most of the run only the upper 6" or so of the condenser would get hot (I'm using a 48" liebig, 3/4 over 1/2), but late in a strip when there's lots of water coming through the condenser would heat about halfway down. That was with winter water temps, about 45 to 50 f set for a very slow trickle. I thought about cutting my condenser down, then remembered what things are like when using 5 gallon buckets of recirc water pumped with a fishtank powerhead. Stuff gets HOT! I need the whole 4' when it's like that.