Opinions appreciated: check valve vs anti-siphon holes in overflow returns

[gregzz4]

I'd like to thank Everyone for their input. I never imagined I'd get this much feedback.

With the limited # of responses to using a check valve, and the thoughts on it fouling etc, that option is off the table.

I am attempting to get some surface flow from the loc-lines. Because of the way I currently have them, there is the chance they can be bumped quite low below the surface, allowing way too much volume to back siphon. I will have to re-think the routing.
This is how they sit and now you see why I originally posted these questions.



I agree whole-heartedly with the idea of laying out the lines so no valve or anti-siphon holes are required.
I'll have to attempt to shorten the lines and it looks like I'll lose the surface flow I was looking for.