Please.... I have a shallow well. Recently, my pump takes too long to prime. I have water in my lines, but when them pump calls for water, I hear air in the pipes from both the pump and the faucetts and it takes too long to catch the prime. I have been told that it could be the foot valve. In the past, if my well level is low, I have water first and then it could loose its prime. Now, it's opposite. I don't have prime (hear the sucking sound) and then the water comes and the pump shuts off after about 2 minutes (vs. 15 sec.when all is good). Foot valve?