I pull water from a lake and pump it up to my cottage. For some
reason, my pump has started short cycling. I changed the pressure
switch, and the pressure tank is fully charged (about 38 lbs). It is
primed. If I open the prime port and turn the pump in it shoots water
high into the air - getting water is not the problem.

When the pump comes on, it quickly builds pressure to 40 lbs and then
shuts off, pressure immediatley drops to 20, pump comes on, then off
very rapidly. Would a leak in the line between the jet pump and the
house cause this? I am thinking it might have frozen and split....