<a href=showthread.php?s=&postid=13130882#post13130882 target=_blank>Originally posted</a> by SuperNemo
Bean,
Wouldn't the system fail if the water level rises above the just terminate line on the syphon tub.
No. The system is designed with several FAIL-SAFES. That is the whole idea.
The emergency standpipe is at a higher intake level than the siphon standpipes intake. If you were to "overfill" the sump and thus submerge the siphon outflow further than normal AND it did not autostart at first.... The overflow box will fill until the EMERGENCY STANDPIPE kicks in. At the same time, the extra water level in the overflow box will more than likely kick start the siphon standpipe.
If you run your system properly, then this is never a concern, though you are still covered with the fail-safe nature of the setup.
So then the just terminate line cannot be more than the distance of the 90s length, i think about slight below an inch or else the pressure from the overflow would not be greater than that of the just terminate line.
You are not understanding the physics here. Even though there is air trapped inside the pipe, air compresses, water does not. In any reasonable scenario, water WILL begin to flow over the siphons weir and will induce a siphon. If it does NOT, then you did not properly setup the system.
How can you guarantee that the just terminate line will always be just below the water level and not more or less due to evaporation or excess was addition during water change?
You are making this out to be much more precise/finicky than it really is. Furthmore, the input side of the sump
should be designed so that the water level is static (that is what baffles do). In a very LARGE sump with NO BAFFLES, the water level fluctuates very little due to even large volumes of evaporation.
In other words, the system is very self tuning and very fail-safe. It can be adapted to fit almost any scenario. If you design without regard to the operation, then of course you can get it to fial, but that holds true for ANY system.