Just had solar heater installed yesterday for my 14x28 inground pool in El Paso, Texas.  I'm currently running your PL2605 variable speed pump (excellent unit by the way!).  I used to have the three steps set as follows:  Step 1 - 1100rpm for 18 hours, Step 2 - 2600rpm for 4 hours and Step 3 - 3100rpm for 2 hours.  Running it this way around the clock really kept the water clean, chemicals balanced, energy bills manageable etc.  However, with the solar heater installed, I have to run the pump at least 2350 rpms or the solar system sucks in air.  I feel I'm losing all the advantage of the variable speed pump becasue I can't run it at low speeds anymore and its going to get expensive.  I could run it at the 2350 for about 8-10 hours during the day to keep the water circulating through the heater so the water stays warm and shut down overnight I guess.  Could you offer any other suggestions to take advantage of the variable speed pump but still have the advantage of the pool heater without running it so fast?