Thank you for the kind words. You can't tell if a heat pump is running by the water temperature difference between the inlet and the outlet pipes. Sometimes you can't even feel the difference with your hand. It all depends on the water flow, heater size and outside temperature among other things. Maybe your water pump is putting out 30 gallons per minute and your have a 3 degree temperature difference. Maybe your water pump is putting out 100 gallons per minute and you have a 1 degree temperature difference? The pool will heat up in the same amount of time but you will never feel the 1 degree. The best way to tell if the heater is working is to measure the outside air and then the temperature of the air blowing out of the top of the heater after about 5 minutes of having it run. You should see about 10 degree drop in temperature. That is not an exact rule but is pretty close for most heaters on most swimming days. I hope that helps. Have a great season.