Return Line Siphon Break

[whatcaneyedo]

I've only ever seen lower output holes used for closed loop and not a return lines for this very reason. However you could still add a syphon break... but the plumbing won't look very pretty. Here is an idea I sketched out. If I was more ambitious I'd learn google sketch but not today. Good grief this looks awful... But anyways, just close the ball valve most of the way to only allow a trickle through. When the power goes out that top part will break the syphon.

[intarsiabox]

You could just put loc-line on and direct it so that the output is just below the water's surface.