Oh yeah, I would most certainly not only use a check valve, but also a bib so *I* control the water going into the pool, nothing automated.

I figure I would only "fill" the pool with the pump off.

I have a Jandy check valve between the filter and the heater/heater bypass valve and a flap check valve just after the heater before the heater outlet valve (that valve along with the inlet side 3-way will allow me to shut off the heater on both sides for servicing without affecting the operation of everything else).