In Amel's installation the water coming out of the "bolt thing" IS the anti-syphon vent. There was no additional vent at the top of the loop, that would be redundant.
All you need is one hole up near the top of the loop-somewhere-so air can get in when the engine stops.
---In amelyachtowners@..., <ryan.d.meador@...> wrote :
That is good news! Just so I'm certain I understand, the water coming out of this bolt thing is normal, and that is distinct from the vent at the top of the loop? I see no path for water from the top of the loop to get into the scupper.