Have you thought about buying a solar heater? They make a big difference in the temp of a pool - especially if you use a solar cover at night to keep from losing heat. Your post doesn't say where you live. I live in Charleston, WV and by using the solar heater and solar cover, we have been swimming since the beginning of May. In the middle of the month, we got a few cold nights and lost a little heat, but quickly rebounded. My water temp today was 84. Just about perfect!