Warm fuzzy

Gentlemen, just finished replacing my pressure gauge. It was zero'd on 40 psi. Now I THINK it is back to normal. Was a little concerned about my operating pressures though. 50/80 psi. Had a new diaphram tank installed last July for a rust leak. He installed a 85 gallon Challenger and set tank to 75 psi. Switch is a 40/60 Square "D". Pump is a Dempster M300 15 GPM 3 HP. I am in the Trinity in Austin. Well hole is at 850, pump at 640 and static water at 523 when drilled 4 years ago. I think 80 is too high and 30 spread too much. I "seem" to remember wellman saying he set it to 50/70. Any thoughts here??

Don't know about whether that's too high, but your air charge should be about 2 pounds less than the turn-on point of the pump control switch. A 20-pound spread is normal, and the tank should be happy as long as the precharge is right.