HOB Overflow Question

[tygger]

My tank is a reef ready tank (drilled with bulkheads) and I was wondering how you guys with hang-on-back overflows deal with power outages?

When the power comes back on, do the hob overflows continue the siphon?

 

[katchupoy]

Yes... The HOB is designed to keep the water inside the U-Tube even without power. This is a common misconception about HOB. But yes, they work even if there are power interruptions...

 

[danch]

I've been testing my plumbing set up with mine. The only time I lose syphon is when I physically pull the syphon tube to simulate a clogged tube.

 

[sjm817]

To lose siphon, enough air must be introduced in the siphon tube to break it.

1) The overflows are designed so that both ends are always submerged. No air can enter the U Tube even when power is off.
2) water moving over the weir creates/carries air bubble that do flow into the siphon tube. This must be dealt with. The air bubbles must flow through the siphon tube and not be allowed to collect.
3) some overflows do a very good job preventing this from occurring, some very poor.