Also another note.. I have a HOB eshopps overflow.. no air lifter needed, and its designed that it cant break siphon.. its actually quite simple really.. the one you have is a sure fire way to flood, the new designed eshopps ones, genious.. umm.. here.. lets explain:
See the black overflow section, if water level falls below there, it cant pull anymore water and sits idle, while the other side has its own little box there, so it cant have air fill there as the drain side over draws leaving a air space.. I havent heard of anyone having a issue with this setup asides from the same flood anyone can get, of not cleaning out your hard lines once in awhile that drain into your sump.