Siphons in Tanks/Sumps

[SofaSnorkeling]

Hello all, fairly new here. I have a VERY basic understanding of how siphons work... flow from higher, over a hump to lower started w sucking.

Where do siphons usually exist in a typical tank/sump setup? Just in the overflow? What problems can arise here, air? What does air do in a siphon?

Where else are undesirable siphons seen in setups and how can they be avoided. Thanks!

 

[mcgyvr]

The 2 common places that siphons occur is the overflow box and sometimes people create one with their auto top off system.
The first is beneficial. .The second is not..


https://en.wikipedia.org/wiki/Siphon

 

[Bruce51]

Learned that one the hard way, my ato water level was higher than the sump lvl of return pump, first the ato water would siphon into the return pump chamber, and at sum point the siphon would reverse and tank water would siphon into my ato reserve. solved the problem by making sure the ato outlet was above the water level of the ato reserve.