Another 'Siphon Break' Question Please?

[Dougal]

Why is it, that the actual LOOP of a siphon break must be above the water line, and not just the exiting vent tube?

 

[RichardS]

Why is it, that the actual LOOP of a siphon break must be above the water line, and not just the exiting vent tube?

What with heel angle, boat loading, wave duration and height etc, I don't think you can determine things that accurately. Installing the loop, or at least part of it, above the estimated water line gives some margin for error.

Richard

 

[BabaYaga]

Why is it, that the actual LOOP of a siphon break must be above the water line, and not just the exiting vent tube?

In my view, because you want air to enter the loop in order to break the siphoning. If the water line/level is somewhere in the vent tube, siphoning can go on undisturbed below it.

 

[VicS]

Why is it, that the actual LOOP of a siphon break must be above the water line, and not just the exiting vent tube?

Because if the loop is below the waterline there will always be a positive pressure in it so air would not be drawn into the loop to break the syphon. If only the vent tube extended above the WL you would simply end up with water in it up to the WL