Prototype 1A Using a grill to heat a pool. The device heats water 30 to 35 degrees at 3 to 4 gallons per minute flow. I find I get a 7 degree increase in my 8000 gallon pool for each 5 gallon tank of propane. Each tank will burn for about 13 to 15 hours on high. A pool cover is required. Thanks Sean! Link.