A check valve is an inline device that usually has a "flapper" that is open (because of suction pressure) if flow is coming through, and closes (by gravity and/or water pressure) if flow stops. This allows water flow in only one direction. They are available at many hardware stores and are not very expensive. Some have springs instead of a "flapper". I paid a little more for ours so they could be opened easily and cleaned. They have a clear side for viewing the working parts. The down side of check valves can be that in the long run, they can get algae and gunk on them, and then not seal as well when you need them to. So you could place a ball valve before the check valve, then the check valve and then another valve and/or the pump. Sounds complicated perhaps, but it really isn't. I just don't like getting wet if i do not need to
Russ Peters has these in operation at his store, if that is close enough for you to get to and you want that "visual" to get the idea. You can also see this application with ball valves, and check valves and hose bibs on the PVC Lines in the pictures of our pond build here on bito.
A hose bib I am describing is just like what you hook a hose up to on the side of the house. But in the PVC Pipe, and it has a different thread than normal PVC threaded fittings. We placed a "double female" hose fitting on the end which allowed the male end of a hose to be attached, which allowed us to fill the line with a normal hose.
Again, these parts are all available at most hardware stores . This all sounds harder than it is when written out in long form. The important thing is the concept of what you are trying to do. The pump you are looking at will work above water like you want it to, just have to do a couple things to make it workable.
