We were camping in Maine at a summer house. The pipes are drained every fall and antifreeze put in toilets. this year we cannot seem to get the air out of the cold water pipes. We filled the plumbing and ran all faucets,tub, and toilet. Air comes out for abourt 5 minutes we keep running every thing for about another 10 minutes. Usually that gets all the air out. This year the air is comming back in the pipes. When we flush the toilet has air on refill, When we run water, air comes out first. How is the air getting back into the pipes. The water is coming from a well drilled outside. Can a water pump pump air if there is not enough water?