I went and look but I defiantly need to clean it off so I am going to do that and look for the arrow thanks!Three blue circles are around the union. The suspected check valve is in the big blue circle in "welll pipe.jpg". A check valve would have an arrow pointing away from the casing.
The arrow might be cast into the underside. So rinse that off, and if you don't see an arrow, use a mirror. If your cellphone can work that close, maybe you could take a photo from below.