New shallow well pump,I prime pump and it runs then pumps water then air then water then air.Well is not deep and is next to large river so out of water shouldnt be problem.How can I check foot valve if the well has one.I plan on pulling it this weekend to see if pipe is in water and if it has a foot valve.Any thing else i should check.Old pump worked great for three years then this problem started so replaced 10 year old pump but still not working.All plumbing from well to pump is all new.