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

[gregzz4]

Originally Posted by Myka

I didn't mind your first idea, but this looks good to me too. IME, the loc-lines are pretty stiff so you really have to give them a good knocking to move them. You can always do test runs with the lines lower to see if there is room in the sump. If your sump can handle the flow with the loc-lines at their lowest point then you're covered anyway.

Thanks, glad to hear that.
IME the L-L will stiffen over time but is quite easy to move right now as it's new.
I had tested the first setup, hence the concern . This version will have to wait a bit for a test as I'm hoping the next time I fill the system it will be with RO water.