Originally Posted by
combatwombat
I really want to understand this, and I think I'm still not getting it. If I install a tee, standpipe, and air admittance valve where shown in my drawing above, it will stop siphon, but not until the water level in the pond reaches the same level that the top of the tee is at. If the tee is 2' below pond water level, then the line will continue to siphon until water level drops 2' and air can be introduced to the main line.
Is that right? Or am I still not getting it?
Bonus question: Anyone have a clue why a 5/8" hole would be insufficient to immediately break siphon on a 2" line? Seems general wisdom is that a 3/8" hole is as big you'd ever need and 3/16" is more common.
The outlet of the pipe inside the pond is 4.5' deep and I drilled the hole at the high point of the line, so it is completely exposed to air. It does work in that the siphon is broken eventually, but it takes about 15 minutes of draining at what looks like about 1-200 gph before it stops completely. Not the end of the world, but I thought it should work a lot faster than that.
I don't think it's just draining the water beyond the high point because there's only about 10' of pipe from the siphon breaker hole and the pump vault, so there should only be about 2 gallons of water to drain back after siphon breaks.