So I've began my plumbing for my sump. My friend suggested buying a pvc inline check socket. What are the pros and cons with having it after my return pump line? Would you recommended that ball valve is safer and better in the long run?
With a properly designed return you should never need a check valve. Check valves are usually a false sense of security and will fail eventually, not if but when. It does not have to be a catastrophic failure either, even a grain of sand or piece of food will prevent it from seating and flood over time.
Keep the return(s) close to the surface of the display and provide plenty of freeboard or excess capacity in the sump and flooding is never an issue. Usually the only time I see a check valve is either a retrofit of an existinmg system or a poorly designed system and I cringe when I see them as the odds are against them.
Yes, always put a ball or gate valve on the discharge side of your return pump so you can throttle the flow for fine tuning with your overflow box and for maintenance. A union or removable joint and a short section of vinyl tubing to break up vibration and sound transmission are also good ideas.