I have a 30' hand drove shallow well, recently I began losing prime over night and then in a few hours. I installed a new check valve ahead of pump but did not fix problem. I then installed a 1" black poly pipe inside old well pipe with new 1" check valve. Primed pump and started to pump a good flow of water but as soon as I shut off pump water ran back to well completely draing pump. I did this several time s with three different check valves. I have two wells four' apart for my lawn sprinklers that have been working fine for eight years. I shut both pumps on and off manually and do not have a tank or presure switch. The wells works fine as long I do not shut them off they will run for hours with good water production.