We had a warm spell over the weekend down here in Tucson so I fired up the gas heater to go swimming. The pool water was ~48 degrees prior to turning on the heater and I started the heater going at ~6:00AM (granted it was probably in the mid 40's that early in the morning). It's a new Sta-Rite 400k BTU heater and it would only raise the water temp by about 3 degrees per hour. It took until about 4:00 in the afternoon to reach 80 degrees. This is the first time I've tried to heat the pool from so cold to so warm and I was honestly expecting a 400k BTU heater to do it quicker than that. Am I expecting too much?