Why the check valve installed on the discharge, but not installed on Suction?

A little confused here.

First, what check valve? What discharge? What suction? And what does any of this have to do with Universities & college, which is the forum you put this question in.

A bit more info needed.

Hi, emptyfree!

A check valve on what, please? Also, if this might be concerning something that you need to answer for a class that you're taking somewhere, it would be helpful to know that. I wonder about that because of the particular forum topic area where you've posted it.

Thanks!