I did keep 2 of my gravity feed lines blown out this winter but there weren't many times that I was able to pump water cause it was so cold, and it took 24hrs to raise the pond 2 inches.
By the end of the winter both water lines had froze up while I was pumping water.
I checked my weather station log and it was below zero 19 of 31 days in Jan., so you see part of the problem, and we didn't have any real thaw this winter.
