He did not post check valve is 15' down but 15' to water. In the summer remove cap, install check valve to threaded pipe then use pipe elbow to Union this to pump. Usually after priming good to go throughout summer. Occasionally if in full sun and a month has gone by water in pump may evaporate and a cup of water to prime may or can be needed but not the original amount needed to draw water up sections of pipe to check valve. In fall remove union, unscrew check valve and pipe with other end of union off well head. Screw cap on well head. Is usually what is the procedure. Also with other check valves this can easily be used on other wells with the union, easy on and off. The biggest priming is the initial priming to bring water to check valve.
The reason check valve is removed is to allow water to recede down to point. This keeps water from freezing and bursting, splitting pipe/well.