hi folks! for my tub, near the master bedroom, i'm hoping to keep pump noise way down by using a low flow rate, maybe even lower than the exorbitant variable-speed pumps will go. i calculated that 5 gpm at 30KBTU/hr would give me a nice temperature rise in the 5 gallons of 12.5 degrees F. the ray-pak heater has a pressure switch 062237B, which if i am reading the manual correctly, seems like putting a 20 GPM floor on the flow rate. the manual even says hi-lo pumps may have to run in high to turn the heat on. how can i heat the tub with such a slow flow and not give up the safety of the pressure switch? perhaps there is another kind of more sensitive pressure switch i can install?