Unions allow maintenance access to piping without having to cut the pipe. I use unions on both sides of every section of pipe so that I can disassemble and drain each section for winter. Imagine having to remove that pump for whatever reason without that union in place.
Looks fine to me. Actually that set up will handle vibrations from the pump better than straight pipe will. I have a similar "loop" connected to my house water pump. At least you didn't forget the union fitting. :D
