As stated above, don't rely entirely on that check valve, I had one stuck and luckily I was around to prevent a flood.
Be sure to make small hole on the return pipe output, a cm below water level, in case the check valve fails when water line goes below this small hole it will pull air producing a siphon break.
Here is a picture, not mine but just as an example, you can see the small hole above the return pipe output.
If you have a syphon break then the check valve is not needed at all. The more unneeded stuff the more that can go wrong and creates unneeded resistance.
Forget both of them, they don't do a thing but make you feel warm and fuzzy.
Place your returns close to the surface so only a very small, easily calculated amount of water siphons back to the sump before the return is exposed and make sure you have at least that much freeboard in your sump at all times. No maintenance, nothing to fail, no noise and it cannot fail. It does not get any more foolproof or simple as an air gap, the best form of backflow prevention known to man.
I cringe every time I see a check valve or drilled hole since both can and do fail no matter how much maintenance, I could defeat one or both in about 3 seconds, they are a waste of money and time and a false sense of security. I couldn't sleep at night with either one or both for that matter.