lifereef restart siphon????

[jb1]

how does a lifereef overflow restart its siphon or any other overflow for that matter. i know a cpr uses a powerhead to pull air out and restart but how do u tube overflows do it.
and how about a tidepool s.o.s. overflow work?
i'm fixing to purchase an overflow and do not want an overflow that does not start the flow after a power loss.

 

[broomer5]

As long as both ends of the U tube are always under water - it will not lose its prime ( ability to siphon )
Lifereef and other quality external hang on overflows accomplish this by their design.
The inner box holds water even when/if the display tank level drops below the teeth.
The outer box has a small acrylic chamber that the end of the U tube extends down into. This chamber fills with water, and remains full ... even when the return pump in the sump is off.
Both ends of U tube are always under water.
When the return pump is turned back on - siphon continues.
Very reliable.
The only times I've seen a U tube lose it's prime;
1) Is if the flowrate is too low. If the return pump in the sump is "undersized" for the tank / overflow ..... and does not provide enough flowrate of water ... it's possible to have very small air bubbles accumulate in the uppermost curve of the inverted U tube.
These small air bubbles form one large bubble.
After a period of air accumulating - this large air bubble can reach both sides of the curve.
If this air pocket reaches both legs of the U tube ( one going to inner box - the other going to outer box ) then the prime will be lost and the U tube will empty out it's water.
This is bad - and will cause the display tank to overfill and the sump to run dry.
2) Cheap designed overflows - that do not have the chamber in outer box that holds water.
Otherwise - very reliable

 

[dreeves]

What he said above...
The Tidepool works the same way as a U tube...the SOS has a cap with a ridgid airline in it to adjust for vacume to reduce the noise...similar to a Durso standpipe.

 

[randy 12]

CPR now uses a small water pump instead of a powerhead. It looks like a small air pump. But instead of blowing air out, it sucks water and air in from an airline tubing (from the nozzle on top of the overflow )and has another airline tubing putting the water and air (it just sucked in) out into the aquarium. I like it much much much better than the powerhead way. They recommend a AquaLifter brand water pump. It's really quiet.
The only time I have seen a u-tube lose it's syphon is when the pump isn't strong enough or when someone says... I saw a bubble in the tube so I lifted it out of the water to release it. Honestly, I have heard this from people.